Area Affected
Roots
Stem / Sheath
Leaf
Panicle / Grains
Whole plant
Cultivated field

Damage Caused by Ants and Termites

Importance of the problem	Ants are minor pests of rice. Damage by ants mainly occurs in upland rice. And the seedling stage is more susceptible to ant attack. Ants eat the seeds thereby affecting germination and resulting in loss of plant stand. The damage is normally very less and no management practices are generally recommended.
Common signs and symptoms	Mainly occur in upland rice Missing rice seeds No plants or missing plants Loss of plant stand Patchy distribution of damage in the field Increase the incidence of diseases vectored by homoptera
Problems with similar symptoms	Symptoms of damage by ants like missing rice seeds, no plants or missing plants and loss of plant stand are also feeding symptoms of the mole cricket.
Causal organism and their spread	Adult ants are causing damage. Adult ants have reddish brown body with brown head. They have mandibular teeth. The queen ant usually lays 75 to 125 eggs in a cluster. Their pupae are whitish in color and they develop in the nests. Ants are hosts to nematodes, fungi, phorid flies, strepsipterans, and eucharitine wasps. They are also preys to natural enemies like birds, snakes, bull frog, and ground lizards.
Mechanism of damage	Ants cause damage by feeding seeds using their sclerotized mandibles. Feeding damage caused by ants occur during the seedling stage of the rice crop.
Ideal management strategy	A cultural management, which is available against ants, is to increase seeding rate. Drench the affected portions with chlorpyriphos @ 5ml /liter
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Army Worm Attack in Rice

Importance of the problem	Army worm is a sporadic pest causing occasional damage to rice plants. The insects multiply in large numbers during certain seasons and causes large outbreaks. The main damage caused is defoliation resulted from heavy feeding. And when the insect population becomes very large complete loss of crop can results.
Common signs and symptoms	Fed-upon leaf tips or along leaf margins Fed-upon whole leaves leaving only midribs Cutting off leaf tips, leaf margins, leaves and even the plants at the base Removal of whole leaves and plants Mature panicles are cut off from the base of the plants. Sub-spherical and greenish white to white rounded eggs either bare or covered with a thin layer of blackish felt Grass green young larvae with dorsal stripes feeding on leaves
Problems with similar symptoms	The symptom damage can be confused with feeding damage caused by cutworms.
Causal organism and their spread	The larvae of army worm (Mythimna separata, Spodoptera mauritia acronyctoides, Spodoptera exempta.) cause the damage. The adult is either grayish black with black markings on its forewings or pale red-brown with fewer markings on the front wings or it has pale red-brown forewings with two pale round spots. Its hindwings have two colours, dark red-brown on top and white underneath or the hindwings are lighter than the forewings. The insect has a body length of more than 15.0 mm. The pupa is 13.0 to 20.0 mm long. It is dark brown. Young larvae have two pairs of prolegs. They have brown to orange head with an A-marking on the frons. They are grass green with gray dorsal stripes. The body of mature larva has shades of green, gray, brown, pink, or black with dorsal or subdorsal longitudinal light gray to black stripes or clear yellow stripes running along the entire length of the body. Two rows of C-shaped black spots are either present or absent along the back. They are 31.0 to 45.0 mm long. The rounded eggs are either bare or covered with a thin layer of blackish felt and are laid in oblong clusters. They are subspherical and greenish white or pearly white. They turn yellow or dark brown with age. A maximum temperature of 15 °C favours adult longevity, oviposition period and egg output and hatching of armyworms. Periods of drought followed by heavy rains sustain the development of the insect pest. Naturally fertilized plants can produce more offsprings. Likewise, the presence of many alternate hosts can fully support the continuous development of the insect pest. The rice insect pest is polyphagous. Aside from the rice plant, it also feeds on bamboo, barley, cabbage, castor, cotton, cruciferous vegetables, flax, jute, maize, mungbean, oats, sorghum, sugarcane, sweet potato, tobacco, wheat, Cynodon dactylon (L.) Pers., Cyperus sp., Echinochloa sp., and Imperata sp., Poa sp.
Mechanism of damage	The larvae feed on the crop by removing large portions of leaf epidermis using its mandibulate mouthparts.
Ideal management strategy	Parasitoids such as tachinids, ichneumonids, eulophids, chalcids, and braconid wasps parasitize this pest. Meadow grasshoppers, ants, birds and toads feed on the pest. Fungal diseases and a nuclear polyhedrosis virus also infect the larvae. Chemical control may be needed when populations are extremely high. Apply carbaryl, endosulfan, trichlorphon, fenthion or methyl parathion as soon as the caterpillars are noticed.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Bacterial Leaf Blight Disease in Rice

Importance of the problem	Bacterial blight is one of the most serious diseases of rice. Appearance of bacterial ooze that looks like a milky or opaque dewdrop on young lesions early in the morning confirms the disease. Yield loss due to this disease corresponds to the plant growth stages at which the rice plants were infected. The earlier the disease occurs, the higher the yield loss.
Common signs and symptoms	Water-soaked to yellowish stripes on leaf blades or starting at leaf tips then later increase in length and width with a wavy margin Appearance of bacterial ooze that looks like a milky or opaque dewdrop on young lesions early in the morning Lesions turn yellow to white as the disease advances Severely infected leaves tend to dry quickly Lesions later become grayish from growth of various saprophytic fungi Seedling wilt or kresek • Observed 1-3 weeks after transplanting • Green water-soaked layer along the cut portion or leaf tip of leaves as early symptom • Leaves wilt and roll up and become grayish green to yellow • Entire plant wilt completely Yellow leaf or pale yellow of mature plants • Youngest leaf is uniform pale yellow or has broad yellow stripe • Older leaves do not show symptoms Panicles sterile and unfilled but not stunted under severe conditions
Problems with similar symptoms	Infected plants show kresek, which resemble rice stem borer damage.
Causal organism and their spread	The bacteria causing the disease are rods, 1.2 x 0.3-0.5 µm. They are single, occasionally in pairs but not in chains. They are Gram negative, non-spore-forming, and devoid of capsules. Their colonies on nutrient agar are pale yellow, circular, and smooth with an entire margin. They are convex and viscid.
Mechanism of damage	Leaf tips of seedlings cut before transplanting and leaf injuries serve as important sources of inoculum especially for kresek. The bacterium or pathogen enters the leaf tissues through natural openings such as water pores on hydathodes or stomata on the leaf blade, growth cracks caused by the emergence of new roots at the base of the leaf sheath, and on leaf or root wounds. Once the bacterium enters the water pore or any opening, it multiples in the epitheme, into which the vessel opens. When there is sufficient bacterial multiplication, some bacteria invade the vascular system and some ooze out from the water pore.
Ideal management strategy	Practicing field sanitation such as removing weed hosts, rice straws, ratoons, and volunteer seedlings is important to avoid infection caused by this disease. Likewise, maintaining shallow water in nursery beds, providing good drainage during severe flooding, plowing under rice stubble and straw following harvest are also management practices that can be followed. Proper application of fertilizer, especially nitrogen, and proper plant spacing are recommended for the management of bacterial leaf blight. The use of resistant varieties is the most effective and the most common management practices Fallow field and allow to dry thoroughly is recommended. Application of bleaching powder in the field is effective Spraying of Streptocycline is found effective.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Bakane Disease of Rice

Importance of the problem	Bakanae is primarily a seed borne disease. Infection usually occurs during seedling and tillering stages of the rice crop. The infected plants show abnormal elongation of plants in seedbed and field. Thin plants with yellowish green leaves and pale green flag leaves confirms the disease. Crop losses caused by this disease may reach up to 20% in outbreak cases.
Common signs and symptoms	Infected plants are several inches taller than normal plants in seedbed and field Thin plants with yellowish green leaves and pale green flag leaves Dying seedlings at early tillering Reduced tillering and drying leaves at late infection Partially filled grains, sterile, or empty grains for surviving plant at maturity In the seedbed, infected seedlings with lesions on roots die which may happen before or after transplanting
Problems with similar symptoms	There is no other disease with similar symptoms as the bakanae disease of rice.
Causal organism and their spread	The fungus Gibberella fujikuroi commonly called as Fusarium moniliforme causes the disease. Bakanae is primarily a seed borne disease. Sowing un-germinated seeds in infested soil gives rise to infected seedlings. Soil temperature of 35ºC is most favorable for infection. Application of nitrogen favors the development of the disease. Wind or water easily carries the spores from one plant to another. High temperature, ranging from 30 to 35ºC favors the development of the disease. Wind or water easily carries the conidia from one plant to another.
Mechanism of damage	The seeds are usually infected during the flowering stage of the crop. Severely infected seeds are discolored because of the conidia of the pathogen. Discolored seeds give rise to stunted seedlings, whereas infected seeds without discoloration produce seedlings with typical bakanae symptoms. Infection may also take place through spores and mycelium, which are left in the water used for soaking seeds. The fungus infects plants through roots or crowns. It later becomes systemic, i.e., it grows within the plant but does systemically infect the panicle. The microconidia and mycelium of the pathogen are found to be concentrated in the vascular bundles, particularly the large pitted vessels and lacunae of the xylem vessels. The pathogen produces gibberellin and fusaric acid. Biological studies of the two substances showed that fusaric acid cause stunting and giberrellin causes elongation.
Ideal management strategy	Clean seeds should be used to minimize the occurrence of the disease. Salt water can be used to separate lightweight, infected seeds from seed lots and thereby reduce seed borne inoculums. Seed treatment using fungicides such as thiram or benomyl is effective before planting. Benomyl or benomyl-t at 1-2% of seed weight should be used for dry seed coating. However, rapid development of resistance against benomyl and carbendazim have been observed which may be caused by successive applications as a seed disinfectant. Triflumizole, propiconazole and prochloraz were found to be effective against strains that are resistant to benomyl and combination of thiram and benomyl.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Birds in Rice Fields

Importance of the problem	Birds squeeze the milky grains and feed on the grains. The damage due to perching of birds on the panicles result to crop loss. At grain maturation, birds often remove entire grains. Similarly, when seeds are sown birds come in large numbers and eat the seeds. Thus, an understanding on the nature of damage by birds is very much important to adopt appropriate management.
Common signs and symptoms	chewed grains milky substance covering the grains empty grains missing grains at maturity whiteheads nests near crops footprints and feathers
Problems with similar symptoms	Whiteheads are also damaged symptom caused by stem borers. In bird’s damage, not all grains are chaffy. In stem borers, all grains in a panicle are chaffy and the panicle can be pulled out easily.
Causal organism and their spread	The common birds that cause damage to our rice fields include, Scaly breasted munia, White-rumped munia, White-headed munia, Chestnut munia, Baya weaver etc. The adult bird is small, brownish raw umber above with light-colored shafts. The chin is brown; each feather has lighter shaft lines. The upper tail is yellowish olive. The breast, abdomen, and other underparts are white in color, each feather with an exposed broad brown band surrounding the white median streak. The brown band is partly surrounded by a somewhat U-shaped white band, with a portion of its free arms covered by the overlapping feathers. The white band is continuous into a whitish buff fringe. The male and female sexes are similar. The attack is severe when the reproductive period of birds coincides with the ripening stage of the rice crop. Staggered planting also emphasizes bird damage.
Mechanism of damage	Birds squeeze the milky grains and feed on the grains. The damage shows milky white substance covering the grains. At grain maturation, birds often remove entire grains.
Ideal management strategy	One of the management options against birds is to destroy their nesting habitats. Scaring devices and chemical repellents can also be used in the field. To further avoid bird damage, simultaneous planting over large areas should be applied.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Brown Plant Hopper Attack in Rice Field

Importance of the problem	Brown Plant hopper (BPH) is an important pest of rice. BPH is common in rainfed and irrigated wetland environments during the reproductive stage of the rice plant. Feeding damage results in the yellowing of the plants. At high population density of the insect pests, hopper burn or complete drying of the plants is observed. Therefore management of BPH is very important in rice cultivation.
Common signs and symptoms	Hopper burn or yellowing, browning and drying of plant crescent-shaped white eggs inserted into the midrib or leaf sheath white to brown nymphs and brown or white adults feeding near the base of tillers Presence of honeydew and sooty molds in the bases of areas infected Ovi-positional marks exposing the plant to fungal and bacterial infections Ragged stunt or grassy stunt virus disease plant may be observed .
Problems with similar symptoms	Hopper burn caused by the plant hoppers is distinguished from other hopper burn symptom by the presence of visible sooty molds at the bases of the rice plant. Virus infected plants may also be found. Hopper burn is similar to the feeding damage or “bugburn” caused by the rice black bug.
Causal organism and their spread	Nilaparvata lugens commonly called as Brown plant hopper (BPH) is the insect pest. Nymphs and adults of BPH cause damage. BPH adult is brownish black with yellowish brown body. It has a distinct white band on its mesonotum and dark brown outer sides. The adults exist in two forms, macropterous and brachypterous. Macropterous adults or long-winged have normal front and hind wings, whereas brachypterous forms or the short-winged have reduced hind wings. A prominent tibial spur is present on the third leg. The nymph has triangular head with a narrow vertex. Its body is creamy white with a pale brown tinge. Mature nymph is 2.99 mm long. It has a prominent median line from the base of the vertex to the end of its metathorax where it is the widest. This line crosses at a right angle to the partition line between the prothorax and mesothorax. The eggs are crescent-shaped and 0.99 mm long. Newly laid eggs are whitish. They turn darker when about to hatch. Before egg hatching, two distinct spots appear, representing the eyes of the developing nymph. Some of the eggs are united near the base of the flat egg cap and others remain free. The adult females are active at temperatures ranging from 10 °C to 32 °C. Macropterous females can survive more than males at varying temperatures. The adults usually live for 10-20 days in the summer and 30-50 days during autumn. The macropterous forms or the long-winged are more attracted to light trap. The most number of catch occurs during the full moon. High nitrogen levels and close plant spacing tends to favor both the BPH and WBPH increase. Outbreaks of the insect pests are closely associated with insecticide misuse, especially during the early crop stages. These insecticide sprays usually directed at leaf feeding insects disrupt the natural biological control, which favor the BPH development as secondary pest.
Mechanism of damage	Both the nymphs and adults of the brown plant hopper insert their sucking mouthparts into the plant tissue to remove plant sap from phloem cells. During feeding, BPH secretes feeding sheaths into the plant tissue to form feeding tube or feeding sheaths. The removal of plant sap and the blockage of vessels by the feeding tube sheaths cause the tillers to dry and turn brown or a condition called hopper burn.
Ideal management strategy	Use resistant varieties such as Jyothi, Bharathi, Aiswarya, Kanakom, Nila etc. for cultivation. Draining the rice field for 3-4 days is recommended during the early stage of infestation. Nitrogen application can be done in split to reduce BPH buildup. Synchronous planting within 3 weeks of staggering and maintaining a free-rice period could also decrease the build-up of BPH. Apply one of the following insecticides as soon as the yellowing symptom is observed, covering the infested patches and the areas surrounding the patches: Carbaryl, quinalphos, fenthion, carbofuran, monocrotophos, phosalone and imidacloprid. While spraying and dusting, care has to be taken to see that the insecticides reach the base of the plants. BPH is a secondary problem due to insecticide spraying for leaf-feeding insects in the early crop stages. To reduce the risk of hopper burn, application of early season insecticide should be avoided. The common parasites of the eggs are the hymenopteran wasps. Eggs are preyed upon by mirid bugs and phytoseiid mites. Both eggs and nymphs are preyed upon by mirid bugs. Nymphs and adults are eaten by general predators, particularly spiders and coccinellid beetles. Hydrophilid and dytiscid beetles, dragonflies, damselflies, and bugs such as nepid, microveliid, and mesoveliid eat adults and nymphs that fall onto the water surface. Fungal pathogens also infect brown plant hoppers. Apply one of the following insecticides as soon as the yellowing symptom is observed, covering the infested patches and the areas surrounding the patches: Carbaryl, quinalphos, fenthion, carbofuran, monocrotophos, phosalone and imidacloprid. While spraying and dusting, care has to be taken to see that the insecticides reach the base of the plants.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Brown Spot Disease of Rice

Importance of the problem	Brown spot is an important fungal disease of rice. It is observed during the maximum tillering up to the ripening stages of the crop. Damage is important when infection occurs in the seed, causing the formation of either unfilled grains or spotted or discolored seeds, giving rise to infected seedlings. Numerous spots or big spots on a leaf may result in blight, thus killing the whole leaf. Therefore, management of the disease is very much important.
Common signs and symptoms	Infected seedlings have small, circular or oval, brown lesions, which may girdle the coleoptile and cause distortion of the primary and secondary leaves (symptom is called seedling blight) Infected seedlings become stunted or die Young or underdeveloped lesions on older leaves are small and circular, dark brown or purplish brown A fully developed lesion on older leaves is oval, brown with gray or whitish center with reddish brown margin Lesions on older leaves of moderately susceptible cultivars are tiny and dark When infection is severe, the lesions may coalesce, killing large areas of affected leaves. Infected glumes with black or dark brown spots Velvety appearance of lesions on infected glumes under severe conditions Infected grains with black discoloration or with brown lesions Infected young roots with black discoloration
Problems with similar symptoms	The lesions can be similar to blast lesions in certain rice varieties.
Causal organism and their spread	The fungal pathogen Helminthosporium oryzaei causes the diseases. It can survive in the seed for more than 4 years. Infected seeds, volunteer rice, infected rice debris, and several weeds are the major sources of inoculums in the field. Infected seeds give rise to infected seedlings. The fungus can spread from plant to plant and in the field by airborne spores. The disease is common in nutrient-deficient soils and un-flooded soil but rare on rice grown on fertile soils. Disease development is favored by high relative humidity (86-100%) and optimum temperature between 16 and 36°C. Leaves must be wet for 8-24 hours for infection to occur. Yield losses due to brown spot epidemic in Bengal in 1942 was attributed to continuous temperature of 20-30°C for two months, unusually cloudy weather, and higher-than-normal temperature and rainfall at the time of flowering and grain-filling stages. Aside from the rice plant, the disease also infects barley, oats, Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop., Eleusine coracana (L.) Gaertn., Leersia hexandra Sw., Panicum colonum (L.) Link, Setaria italica (L.) P. Beauv., Triticum aestivum L. em. Thell. (wheat), Zea mays L. (maize), and Zizania aquatica (wild rice).
Mechanism of damage	The infection processes start at the formation of appressoria. During this time, there is an increase in protoplasmic streaming in the host cells and the cell nuclei moved near the appressorium. It is followed by the hyphae attacking the middle lamella and penetrating the cells. The middle lamella started to separate and caused the formation of yellowish granules. Then, 2 or 3 cells died and mycelia developed in the cells. Appearance of minute spots followed. Another observation showed that the spores or conidia germinate by germ tubes from the apical and basal cells. Germ tube is covered with mucilaginous sheath and at its tip, an appressorium is formed. The fungus directly penetrates the epidermis by the infection pegs formed under the appressoria. The germ tubes also penetrate the leaf through the stomata without producing any appressorium.
Ideal management strategy	Since the fungus is seed transmitted, a hot water seed treatment (53-54°C) for 10-12 minutes may be effective before sowing. This treatment controls primary infection at the seedling stage. Presoaking the seed in cold water for 8 hours increases effectivity of the treatment. Seed treatment with captan, thiram, chitosan, carbendazim, or mancozeb has been found to reduce seedling infection. Seed treatment with tricyclazole followed by spraying of mancozeb + tricyclazole at tillering and late booting stages gave good control of the disease. Application of chitosan, iprodione, or carbendazim in the field is also advisable.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Calcium Deficiency Disorder in Rice Fields

Importance of the problem

Calcium is a important cell wall constituent. It helps in cell wall stabilization as an enzyme activator, in osmo-regulation, and in the cation-anion balance. An adequate supply of calcium increases resistance to diseases such as bacterial leaf blight and brown spot. The rate of calcium uptake is proportional to the rate of biomass production. Hence, maintaining calcium at ideal level is very much advisable.

Common signs and symptoms

Tips of youngest leaves become white or bleached, rolled, and curled
Necrotic tissue may develop along the lateral margins of leaves and old leaves eventually turn brown and die
Stunting and death of growing point during extreme deficiency

Problems with similar symptoms

Ca deficiency may resemble B deficiency, and plant tissue analysis may be required to distinguish the cause of symptoms.

Causal organism and their spread

Ca deficiency is relatively rare especially in irrigated rice systems. It can be caused by one or more of the following:
• Small amounts of available Ca in soil (degraded, acid, sandy soils)
• Alkaline pH with a wide exchangeable Na:Ca ratio resulting in reduced Ca uptake. Use of irrigation water rich in NaHCO3.
• Wide soil Fe:Ca or Mg:Ca ratios resulting in reduced Ca uptake. Long-term irrigated rice cultivation may lead to higher Mg:Ca and Fe:Ca ratios.
• Excessive N or K fertilizer application resulting in wide NH4:Ca or K:Ca ratios and reduced Ca uptake.
• Excessive P fertilizer application, which may depress the availability of Ca (due to formation of Ca phosphates in alkaline soils).

Ca deficiency is very uncommon in lowland rice soils because there is usually sufficient Ca in the soil, from mineral fertilizers, and irrigation water.

Mechanism of damage

Calcium is a constituent of Ca pectates, important cell wall constituents also involved in biomembrane maintenance. It helps in cell wall stabilization as an enzyme activator, in osmoregulation, and in the cation-anion balance.

Ca is less mobile in rice plants than Mg and K. Because Ca is not retranslocated to new growth, deficiency symptoms usually appear first on young leaves. Ca deficiency also results in impaired root function and may predispose the rice plant to Fe toxicity.

An adequate supply of Ca increases resistance to diseases such as bacterial leaf blight (caused by Xanthomonas oryzae) or brown spot (caused by Helminthosporium oryzae). The rate of Ca uptake is proportional to the rate of biomass production.

Ideal management strategy

The damage is important throughout the growth cycle of the rice crop.
Ca deficiency is relatively rare especially in irrigated rice systems.
Apply farmyard manure or straw (incorporated or burned) to balance Ca removal in soils containing small concentrations of Ca.
Use single superphosphate (13-20% Ca) or triple superphosphate (9-14% Ca) as a Ca source.

Ca fertilizer sources for rice are:

Name	Formula	Content	Comments
Calcium chloride	CaCl₂. 6 H₂O	18% Ca	Soluble, quick-acting, does not raise pH
Gypsum	CaSO₄. 2 H₂O	23% Ca, 18% S	Slightly soluble, slow-acting, for saline and alkaline soils
Dolomite	MgCO₃⁺CaCO₃	13% Mg, 21% Ca	Slow acting , content of Ca and Mg varying
Lime	CaCO₃	40% Ca	Slow-acting, for acid soils

• Apply CaCl2(solid or in solution) or Ca-containing foliar sprays for quick treatment of severe Ca deficiency.
• Apply gypsum on Ca-deficient nonacidic soils, e.g., on sodic and high-K soils.
• Apply lime on acid soils to raise pH and Ca availability.
• Apply Mg or K in conjunction with Ca because Ca may cause deficiencies in these nutrients.
• Apply pyrites to mitigate the effects of NaHCO3-rich water on Ca uptake.

References

1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines
2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Harvest Loss from Threshing, Drying

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Importance of the problem

Harvesting is the process of collecting the mature rice crop from the field. Harvesting consists of cutting, threshing, cleaning, hauling and bagging. Timely harvesting ensures good grain quality and high market value. But many times harvest will be delayed and may result in grain loss. Hence, care should be taken to avoid loss immediately after harvest.

Common signs and symptoms

Grain damage and cracking/breakage
Shattering if grain is too dry
Discoloration
Large amounts of grains still remain in straw after threshing
Threshing and drying will be carried out in field resulting in greater contamination by soil particles.

Problems with similar symptoms

The loss during harvest is a management problem and can be easily distinguishable

Causal organism and their spread

The key to post-production is correct timing of operations, and grain moisture content (MC). Target MC for key post-production operations are shown in the table:

Operation	Desired Moisture Content (MC)	Primary losses
Harvesting	20-25 %	Shattering if grain is too dry
Threshing	20-25% for mechanical threshing <20 % for hand threshing	Incomplete threshing Grain damage and cracking/breakage
Drying	Final moisture content is 14% or lower	Spoilage, fungal damage Discoloration
Storage	<14% for grain storage <13% for seed storage <9% for long term seed preservation	Fungal, insect & rat damage

Mechanism of damage

At harvest time rice grain contains a lot of moisture. At high grain moisture contents there is natural respiration in the grain that causes deterioration of the rice. High moisture promotes the development of insects and molds that are harmful to the grain. High moisture in grain also lowers the germination rate of rice. Therefore, drying of rice is critical to prevent insect infestation and quality deterioration of rice grain and seed.

Ideal management strategy

Crops should be cut when 80-85% of the grains are straw (i.e. yellow) colored. Grains should be firm but not brittle when squeezed between the teeth. The grain moisture content ideally is between 20-25% moisture content. If the crop is too dry, fissures will form in dry kernels and when these are rewetted, they break when milled. In dry season, the optimum time of harvest is 28 to 35 days after heading. In wet season, optimum time is 32 to 38 days after heading.

• Immediately dry paddy after harvest to 18% MC for storage up to two weeks.
• Dry paddy for milling to 14%. Drying below 14% reduces weight and milling yield.
• For 8-12 month storage dry to 13% or less, for long term storage exceeding 1 year to 9%.
• Clean the grains before drying to avoid uneven drying and wet spots.
• Do not mix grain with different MC to avoid cracking.
• Monitor grain temperature and MC to prevent excess temperatures and over-drying.

Storage period	Required MC for safe storage	Potential problems
2 to 3 weeks	14 - 18%	Molds, discoloration, respiration loss
8 to 12 months	13% or less	Insect damage
more than 1 year	9 % or less	Loss of viability

References

1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines
2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Cloddy Soil in Rice Germination

Importance of the problem	Good crop establishment lays the foundation for good yield. Cloddy soil can greatly reduce crop stand in dry direct seeded fields. It’s economic effect can be direct in terms of stand and yield reduction or indirect in terms of increased tillage costs to break down clod size.
Common signs and symptoms	• Soil clods much larger than seed size at planting • Poor crop emergence in dry seeded fields • Pattern of damage is usually general across the field
Problems with similar symptoms	Various problems causing problems of crop establishment (e.g., seed too deep, soil too soft at seeding, poor emergence in low spots in fields, heavy rainfall at seeding, soil crusting, poor seed quality, poor seed distribution, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting).
Causal organism and their spread	Cloddy soil can be a problem in all dry direct sown fields and generally occurs because the soil is tilled when it is too dry.
Mechanism of damage	The seed falls down the cracks in between the clods. As the soil clods break up due to the action or rain or irrigation, the seed becomes covered by too much soil and has problems emerging. In addition, there may be poor soil-seed contact limiting the extent to which the seed can absorb water to begin the germination process.
Ideal management strategy	When soil is tilled too dry, it will typically result in large dry hard clods, which are difficult to break down. For dry direct seeding, tillage is best done when soil moisture is below field capacity and well above permanent wilting point. If the soil is too wet, the soil will seal and smear - too dry and large clods form. Sandy soils can be tilled at a higher percent of available moisture than clayey soils. Secondary tillage should follow primary tillage within a day or two for clayey soils with a little wider window of opportunity for sandy soils. For best results, there should be a range of sizes of soil clods. If the clod size is much larger than the seed, then problems are likely. Rainfall or irrigation can break clod size down.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Cricket in Rice

Importance of the problem	Crickets are small defoliating insects seen in rice fields. They normally feed on seeds, roots, or leaves of young seedlings. As a result of the attack the seed die or fail to germinate. The attack is more noticed during April-May. The control of crickets should be attempted only when the damage is severe.
Common signs and symptoms	Feeds on leaves by making irregular to longitudinal exit holes Cutting of central portions of the leaf blades leaving only the midrib Excessive feeding causes dead heart White to orange, elongate-ovoid eggs Pale brown nymphs and adults feeding on the rice plants
Problems with similar symptoms	The symptoms can be confused with the damage caused by grasshoppers and other defoliating insects.
Causal organism and their spread	The nymph and adults of Mole cricket (Gryllotalpa Africana) causes the damage. Individual eggs are elongate-ovoid. Newly laid eggs are whitish and turn orange with age.The nymph has the same color as the adult. It is a smaller version of the adult except for its wing pads. It has a pair of brown to black spots along its abdomen. The adult cricket is pale brown. It measures 1.0 to 1.8 cm long. It has long antennae and legs. The female has a long and spear-shaped ovipositor. The female is longer in size than the male cricket. Crickets or gryllids are both leaf- and stem-feeding insects. They are active at night. Their nymphs are more destructive than the adults. They are common in the irrigated rice environment. In upland environment, the insects are found underneath heaps of weed piles. Presence of piles of weeds attracts the insect pest. Alternate hosts support continuous presence of the insect pest in rice environment.
Mechanism of damage	Crickets feed on leaves and stems of the rice plants.
Ideal management strategy	Apply carbaryl dust @ 2kg of WP /ha if damage is severe
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Cut Worm in Rice

Importance of the problem	The cutworm is an important pest of upland rice. The pest cause the damage by eating the soft leaves of the rice plant. Full-grown caterpillars devour the entire plant. The outbreaks often occur when heavy rain follows periods of prolonged drought. And when the pest population exceeds 4-5 larvae per square meter, management strategy need to be adopted.
Common signs and symptoms	Young caterpillars cause the damage by eating the soft leaves of the rice plant. Full-grown caterpillars devour the entire plant. The rice plant can be checked for the presence of pearly white and round eggs or brownish black larvae feeding on rice. Likewise, the symptoms can be visually inspected for the presence of cut seedlings and leaves eaten.
Problems with similar symptoms	The defoliation or feeding damage caused by cutworms can be confused with other defoliators or leaf-feeding insects.
Causal organism and their spread	Spodoptera litura, called as rice cut worm causes the damage. The monsoonal rains favor the development of this insect pest. Likewise, the presence of alternate hosts contributes to the insect’s abundance. Outbreaks of the pest often occur after periods of prolonged drought followed by heavy rains. The insect pest is polyphagous and has about 150 host species like cotton, cruciferous vegetables, cucurbits, groundnut, maize, potatoes, rice, soybean, tea, tobacco, Capsicum annum (hot pepper), Colocasia esculenta (L.) Schott, and Phaseolus sp. The adult insect is a moth with dark brown forewings having distinctive black spots and white and yellow wavy stripes. Its hind wings are whitish with gray margins and somewhat irridescent. The adult moths are nocturnal and highly attracted to light traps. During the day, they hide at the bases of rice plants and grassy weeds. Adult lays eggs which are pearly white and round and have a ridged surface. The eggs usually hatch in the early hours of the morning. The newly hatched larvae are tiny and greenish. In fully grown larvae one to two dark spots are visible on the thoracic segments near the base of the legs. The abdominal segments have two light brownish lateral lines on each side. Neonate larvae feed on the leaf tips or from the base of the leaf toward the apical area. At daytime, the larvae are found under leaf litter in the ground in dryland fields. In wetland environments, the larvae usually stay on plants above the water surface. The moth has a black or brown pupa.
Mechanism of damage	The larva feeds on leaves and sometimes cut off the stems.
Ideal management strategy	Keeping fields flooded may keep population of this pest at low levels. Biological control agents of cutworm are very abundant. For example, scelionid and braconid wasps are egg parasitods and grasshoppers are predators of the pest. Fungal and polyhedrosis viruses are pathogens that attack this insect pest. Apply carbaryl, chlorpyriphos as soon as the caterpillars are noticed.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Water stress in Rice Cultivation

Importance of the problem

Rice is one among the few plants that can grow in water. And water is an important input in rice cultivation. A stress in water can cause considerable yield and economic loss in rice production. Water stress is most critical around flowering (from three weeks before flowering up to one week after anthesis). Therefore, adopting a careful water management strategy is very much important in rice cultivation.

Common signs and symptoms

Plants stunted
Leaves roll
Flowering delayed
Tip burn
Leaf senescence
May cause whitehead (though the tiller will still be attached to the stem)

Problems with similar symptoms

The symptoms can be confused with N deficiency and high spots in the field.

Causal organism and their spread

Water stress is a problem in rainfed areas with poor rainfall distribution or within irrigated areas with poor water delivery. Permeable soils (i.e., high infiltration rates) and soils with low moisture retention increase the probability of water stress. Poorly leveled fields often result in patches of higher soil with water stress.

Mechanism of damage

The lack of water in the soil reduces the ability of the plant to extract essential nutrients from the soil. The lack of water in the plant reduces cell expansion.

Ideal management strategy

Water stress can be reduced by ensuring fields are well leveled, by choosing an appropriate cultivar and planting date that increases the probability of moisture being available during the critical flowering period.

The ability of cultivars to tolerate water stress depends on direct tolerance or avoidance based on the length of their growth period. To the extent possible, periods of probable moisture stress should be identified and the cultivar selected to avoid these probable periods of stress.

Categories of irrigation schedule for rice

Schedule	Stages
Schedule	Rooting to max. tillering	Max. tillering to heading	Heading to maturity
Category I	Continuous submergence	Saturation point*	Saturation point*
Category II	Saturation point*	Continuous submergence	Continuous submergence
Category III	Continuous submergence	Continuous submergence	Hair cracking of surface*
Category IV	Hair cracking of surface*	Continuous submergence	Hair cracking of surface*

*Irrigation at 5 cm to be given at the stages marked.

Maintain water level at about 1.5 cm during transplanting. Thereafter increase it gradually to about 5 cm until maximum tillering stage. Drain water 13 days before harvest.
[Note: In areas where water for irrigation is assured and where acidity is high, draining and re-flooding every 15 days are recommended. In flood prone areas, aged seedlings of Mahsuri or other varieties recommended for waterlogged conditions may be planted. The planting may be pre-poned or post-poned to avoid synchronization of the critical stages of maximum tillering or heading with the usual flood period in the tract.]
During the mundakan crop season, water level of 5 cm need not be maintained continuously after the cessation of northeast monsoon. Five centimeter irrigation once in 6 days will be quite adequate for project areas where water is assured.
For summer rice (in situation where the ground water level is shallow, i.e., within 1 m from the surface), 5 cm irrigation two days after disappearance of ponded water is sufficient instead of 5 cm continuous

References

1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines
2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Dry Winds in Rice

Importance of the problem	Dry winds can cause greater loss of water through evapo-transpiration. This in turn causes cooking of leaf tips and drying off symptoms. And many times this will be confused with other deficiency symptoms. However, no management strategy need to be adopted. An awareness of the problem help us in distinguishing it from other problems.
Common signs and symptoms	Plant look healthy except that upper tips of leaves are necrotic (i.e., dead) The effect varies with cultivar Pattern of damage is general across the field
Problems with similar symptoms	May be confused with diseases or nutrient deficiencies that dry the leaf tips.
Causal organism and their spread	The wind burn effect results from the leaf tips drying faster than water can be provided for evapo-transpiration. Thus the leaves essentially cook their tips as they can’t keep them cool enough.
Mechanism of damage	The wind burn effect results from the leaf tips drying faster than water can be provided for evapo-transpiration. Thus the leaves essentially cook their tips as they can’t keep them cool enough.
Ideal management strategy	No management is really required. If some yield loss is expected then a new cultivar may not have the same problem should be used.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

False Smut Damage in Rice

Importance of the problem	False smut is fungal disease of rice affecting the grains. The affected grains will get transformed into a mass of yellow fruiting bodies. Growth of velvety spores enclose floral parts. Only few grains in a panicle are usually infected and the rest are normal. Since, the disease occurs rarely, no control measures is usually recommended.
Common signs and symptoms	Individual rice grain transformed into a mass of velvety spores or yellow fruiting bodies Growth of velvety spores enclose floral parts Immature spores slightly flattened, smooth, yellow, and covered by a membrane Growth of spores result to broken membrane Mature spores orange and turn yellowish green or greenish black Only few grains in a panicle are usually infected and the rest are normal
Problems with similar symptoms	The symptom of the disease is very specific, therefore no other disease exhibits this symptom.
Causal organism and their spread	The causal organism is a fungus Ustilaginoidea virens (Cooke). The disease is favored by periods of rain, high humidity, and soils with high nitrogen content. Wind causes dissemination of the spores from plant to plant. The fungus overwinters as sclerotia and chlamydospores. The primary infection of rice plants begins from the ascospores that are produced from sclerotia, whereas the secondary infection comes from chlamydospores.
Mechanism of damage	There are two types of infection. One type occurs at flowering stage when the ovary is destroyed but the style, stigmas, and anther lobes remain intact and are buried in the spore mass. The second infection occurs when the grain is already mature. The spores accumulate in the glumes. The spores absorb moisture, swell, and force the lemma and palea to open. The fungus contacts the endosperm and growth is observed. The whole grain is replaced with a mass of spores.
Ideal management strategy	No special control measures are necessary. Among the cultural control, destruction of straw and stubble from infected plants is recommended to reduce the disease. At tillering and preflowering stages, spraying of carbendazim fungicide and Propiconazole can effectively control the disease.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Grassing Animals

Importance of the problem	Often areas of rice fields can be seen eaten by grassing animals. Animals like cows, buffalos, goats etc may have eaten the rice plants. The damage can cause problems in crop establishment. Being aware of such problems is very much important to avoid it.
Common signs and symptoms	Areas of rice fields will be eaten in patches by grassing animals like cow, buffalo, goat etc. The foot prints of such animals will be seen in soil near the place of damage The presence of such animals in the area further confirms the possibility of the damage
Problems with similar symptoms	The damage is very much characteristic of the problem.
Causal organism and their spread	Grassing animals like cow, goat, buffalo etc cause the damage
Mechanism of damage	The animals eat the growing rice plants and cause the damage
Ideal management strategy	Have a control over the movements of grassing animals in the field.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Green Semi-looper

Importance of the problem	Green semi-looper is found during the seedling and tillering stages of the rice crop.The green semi-loopers defoliate the rice plants. However, this pest rarely causes economic loss to crops because of compensation. Natural enemies often suppress its populations.
Common signs and symptoms	Young larvae scrape the tissues from leaf blades Mature larvae feed on leaf edges to create notches The presence of the insect pest feeding on the plant will confirm its feeding damage. Likewise, its characteristic form of damage on the leaf can also identify what insect caused such symptoms.
Problems with similar symptoms	The feeding damage of the green semi-looper is similar to that of the rice green hairy caterpillar.
Causal organism and their spread	Rice semi looper (Naranga aenescens) is causing the damage. Both the male and female moths are yellow-orange. Their forewings have two diagonal dark red bands. The yellow eggs are spherical. Mature eggs have purple to violet markings. The larval head and body are yellow-green. White lines run along the entire length of the body. The young pupa is light green and turns brown as it matures.
Mechanism of damage	Both the young and mature larvae feed on leaves. Young larvae scrape the leaf tissues of the epidermis of the leaf blade leaving only the lower white surface. Matured larvae often cut out sections of leaf blades especially in the margins.
Ideal management strategy	Highly fertilized crops may favor larval development. Hence controlled or regulated use of fertilizers in infection prone areas will be beneficial The insect pest is generally managed by natural biological control agents, like small trichogrammatid wasps that parasitize eggs. Ichneumonid, braconid, elasmid, eulophid and chalcid wasps parasitize both the larvae and pupae, and spiders feed on the adult moths.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Heavy Rainfall in Rice Cultivation

Importance of the problem	Heavy rainfall, especially during the initial days of crop establishment can cause much damage to rice plants. The plants will be either uprooted or washed away depending on the intensity of the rainfall. Awareness about the problem can help in adopting proper drainage measures.
Common signs and symptoms	Poor plant stand on direct seeded fields - especially if wet direct seeded Pattern of damage is usually general across the entire field, but may be more obvious in low spots
Problems with similar symptoms	Various problems causing problems of crop establishment (e.g., cloddy soil, seed too deep, soil too soft at seeding, poor emergence in low spots in fields, soil crusting, poor seed quality, poor seed distribution, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting.
Causal organism and their spread	The problem happens when heavy rain falls on freshly seeded fields and is worse if the field has been wet direct seeded. The problem tends to be worse in heavy textured soils.
Mechanism of damage	Seed is washed deeper into the anaerobic layers of the soil creating problems in germination and growth for emergence (i.e., oxygen not available for growth).
Ideal management strategy	The problem tends to be worse in heavy textured soils. The critical period is the first 1-2 days after sowing - with the problem being much worst in wet-direct seeded fields. Surface seeding or good field drainage may help.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Herbicide Toxicity

Importance of the problem	Herbicides are now increasingly used by farmers to control weeds. At times the usage goes beyond recommended level and the plants shows toxic symptoms. This happens mainly because of lack of proper knowledge on dosage and application. And their potential impact on environment is very much serious. Hence, a special cautious approach need to be adopted in herbicide use.
Common signs and symptoms	Poor crop emergence (e.g., if pendamethalin comes into contact with the seed) Root damage (e.g., possibly 2,4-D) Whitehead (e.g., possibly Phenoxyprop)
Problems with similar symptoms	Problems of crop establishment can be confused with other problems such as cloddy soil, seed too deep, soil too soft at seeding, heavy rainfall at seeding, soil crusting, poor seed quality, poor seed distribution, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting.
Causal organism and their spread	The problems typically happen if products are not used according to their recommendations - e.g., at the wrong rate, the wrong stage of crop growth, or sometimes if the product is carried into contact with the emerging seed (e.g., water infiltration moves the product into the soil). Plants vary in their susceptibility both in terms of variety and growth stage.
Mechanism of damage	The effect varies, but damage may occur due to contact or due to translocation within the plant.
Ideal management strategy	The primary management requirement is to firstly determine the pest whether an application is required. Then, carefully read the label of the product and follow the recommendations carefully.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of High Seed Rate in Rice Cultivation

Importance of the problem	High seed rate is often used by farmers to compensate the possible loss due to adverse conditions. But in certain situations the high seed rate itself becomes a problem. When plants are too close together, the stems become weak. It can result in lodging and yield loss during heading. Further, the high seed rate brings certain extend of cost interms of cost of seeds and for weed control. Therefore, we need to have an eye on seed rate in rice cultivation.
Common signs and symptoms	High plant count (e.g., > 250 plants per m2) Plants too close together with thin stems and possibly lodged Number of seed in each 10 cm x 10 cm square multiplied by the thousand grain weight equates to the estimated seed rate (kg per ha) Seed rates are typically adequate between 40 to 100 kg per ha Pattern of damage is uneven in patches across the field
Problems with similar symptoms	Various problems causing problems of crop establishment (e.g., cloddy soil, seed too deep, soil too soft at seeding, poor emergence in low spots in fields, heavy rainfall at seeding, soil crusting, poor seed quality, poor seed distribution, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting.
Causal organism and their spread	Farmers often use high seed rates due to poor seed quality, to compensate for losses to rats, birds and snails and to increase crop competition with weeds. Crops can be surface broadcast (wet or dry); drill seeded (using machines) or broadcast and incorporated when sown on dry fields. Higher seed rates are usually used if seed is broadcast. Pre-germinated seed is typically used when wet direct seeding. Direct seeded fields tend to have greater problems of lodging, especially when the seed is surface sown. For good establishment, the fields have to have good water management and be more level. When broadcast, fields can have patches of either too many or too few plants depending on the skills of the broadcaster and the soil conditions where the seed lands.
Mechanism of damage	If the crop stand is too dense, then the stems can be thin and weak resulting in lodging during heading and grain maturation.
Ideal management strategy	For good establishment, direct seeded fields have to have good water management and be well leveled. Ensure an appropriate seed rate with even distribution of good quality seed (i.e., high germination and vigor). In direct seeded fields, the target number of spikes varies with season and variety but typically ranges from 350 to over 500 spikes per m2. A direct seeded plant will typically give of the order of 2-3 spikes per plants. Thus, crop stand should be of the order of 100 to 200 plants per m2. Seed rates between 40 to 100 kg per ha are usually sufficient, if other factors (e.g., pest problems and seedbed preparation) are not problematic.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by improper drying

Importance of the problem

Drying of grain involves exposing grain to ambient air with low relative humidity or to heated air. This will evaporate the moisture from the grain and then the drying air will remove the moisture from the grain. Since drying practices can have a big impact on grain or seed quality, it is important to understand some fundamentals of grain drying.

Common signs and symptoms

Spoilage, fungal damage
Discoloration
Grain cracking and breakage over milling
Fungal, insect & rat damage
Loss of viability

Problems with similar symptoms

The problem of improper drying is more like a management problem and can be easily distinguished from other problems.

Causal organism and their spread

Storage period	Required MC for safe storage	Potential problems
2 to 3 weeks	14 - 18%	Molds, discoloration, respiration loss
8 to 12 months	13% or less	Insect damage
more than 1 year	9 % or less	Loss of viability

Mechanism of damage

At harvest time rice grain contains a lot of moisture. At high grain moisture contents there is natural respiration in the grain that causes deterioration of the rice. High moisture promotes the development of insects and molds that are harmful to the grain. High moisture in grain also lowers the germination rate of rice. Therefore, drying of rice is critical to prevent insect infestation and quality deterioration of rice grain and seed.

The purpose of drying is to reduce the moisture content of rough rice to a safe level for storage. As even short term storage of high moisture paddy rice can cause quality deterioration, it is important to dry rice grain as soon as possible after harvesting - ideally within twelve hours.

Ideal management strategy

Immediately dry paddy after harvest to 18% MC for storage up to two weeks.
Dry paddy for milling to 14%. Drying below 14% reduces weight and milling yield.
For 8-12 month storage dry to 13% or less, for long term storage exceeding 1 year to 9%.
Clean the grains before drying to avoid uneven drying and wet spots.
Do not mix grain with different MC to avoid cracking.
Monitor grain temperature and MC to prevent excess temperatures and over-drying.

References

1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines
2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Iron Toxicity in Rice

Importance of the problem	Iron toxicity is a common problem noticed in rice fields. This happens mainly when the field is waterlogged for a prolonged period. During such situations the concentration of iron in the soil will go very high. The plant absorbs more iron and the toxicity symptoms will be noticed. Draining the field is the immediate way to reduce iron toxicity. And management of iron toxicity is very much important in rice cultivation.
Common signs and symptoms	Tiny brown spots appear on lower leaves starting from tip and spread toward the leaf base. Spots combine on leaf inter-veins and colour of leave turn orange-brown. Leaves become narrow and colour changes to purple-brown if iron toxicity is severe. Stunted growth, extremely limited tillering and death of affected leaf happens. Coarse, sparse, damaged root system with a dark brown to black coating on the root surface and many dead roots Freshly uprooted rice hills often have poor root systems with many black roots
Problems with similar symptoms	Only iron -toxic plants exhibit these symptoms
Causal organism and their spread	Iron toxicity tends to occur on soils that remain waterlogged. The principal causes of Fe toxicity are: • Large Fe2+ concentration in soil solution because of strongly reducing conditions in the soil and/or low pH. • Low and unbalanced crop nutrient status. • Poor root oxidation and Fe2+ exclusion power because of P, Ca, Mg, or K deficiency. • K deficiency is often associated with low soil base content and low soil pH, which result in a large concentration of Fe in the soil solution. • Poor root oxidation (Fe2+ exclusion) power because of the accumulation of substances that inhibit respiration (e.g., H2S, Fe S, organic acids,). • Application of large amounts of un-decomposed organic matter. • Continuous supply of Fe into soil from groundwater or lateral seepage from hills. • Application of urban or industrial sewage with a high Fe content
Mechanism of damage	Excessive iron uptake results in increased polyphenol oxidase activity. This inturn leads to the production of oxidized polyphenols, the cause of leaf bronzing. Large amounts of iron in plants can give rise to the formation of oxygen radicals, which are highly phytotoxic and responsible for protein degradation and peroxidation of membrane lipids.
Ideal management strategy	Plant rice varieties tolerant to Fe toxicity (e.g., Mahsuri). If nutrients are supplied in sufficient amounts, hybrid rice varieties have a more vigorous root system and higher root oxidation power, and do not tend to absorb excessive amounts of Fe from Fe-toxic soils. Delay planting until the peak in Fe2+ concentration has passed (i.e., not less than 10-20 d after flooding). Use intermittent irrigation and avoid continuous flooding on poorly drained soils containing a large concentration of Fe and organic matter. Balance the use of fertilizers (NPK or NPK + lime) to avoid nutrient stress. Apply sufficient K fertilizer. Apply lime on acid soils. Do not apply excessive amounts of organic matter (manure, straw) on soils containing large amounts of Fe and organic matter and where drainage is poor. Use urea (less acidifying) instead of ammonium sulfate (more acidifying). Carry out dry tillage after the rice harvest to enhance Fe oxidation during the fallow period. This reduces Fe2+ accumulation during the subsequent flooding period.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Leaf Scald Disease in Rice

Importance of the problem	Leaf scald is a fungal disease affecting rice. The disease is important during the tillering and stem elongation stages of growth. The affected areas dry out giving the leaf a scalded appearance. The scald can be easily distinguishes the disease from the other diseases. Management of the disease is based on the extent of infestation in the field.
Common signs and symptoms	Zonate lesions of alternating light tan and dark brown starting from leaf tips or edges Lesions oblong with light brown halos in mature leaves Individual lesions 1-5 cm long and 0.5-1 cm wide or may almost cover the entire leaf Continuous enlargement and coalescing of lesions result in blighting of a large part of the leaf blade The affected areas dry out giving the leaf a scalded appearance Translucent leaf tips and margins Infected leaf tips also split near the midrib especially when there are strong winds
Problems with similar symptoms	Leaf scald can be confused with bacterial leaf blight. A visible scalded appearance of the leaf easily distinguishes the disease from the other diseases. Immersing cut leaves in clear water for 5-10 minutes can identify leaf scald. It is a leaf scald if no ooze comes out.
Causal organism and their spread	A fungus (Microdochium oryzae (Hashioka & Yokogi)) causes the leaf scald disease. Disease development usually occurs late in the season on mature leaves and is favored by wet weather, high nitrogen fertilization, and close spacing. Results of artificial inoculation using the conidial stage showed that the disease developed faster in wounded than unwounded leaves indicating that the fungus is a weak pathogen. The sources of infection are seeds and crop stubbles. Wet weather and high doses of nitrogenous fertilizer favor the disease.
Mechanism of damage	The conidia germinate and produce appressorium-like structures of various sizes upon contact with stomata. The fungus gains entry through the stomatal slits, thereby causing swelling of the stomata cavities. The substomatal hyphae grow profusely into the intercellular spaces and then into the mesophyll cells. About three days after inoculation, short-branched conidiophores grow out from the stomata and produce spore masses.
Ideal management strategy	The only cultural control practice, which is applicable for the disease is to avoid high use of fertilizer. Chemicals such as benomyl, carbendazim, quitozene, and thiophanate-methyl can be used to treat the seeds to eliminate the disease. In the field, spraying of benomyl, fentin acetate, edifenphos, and validamycin significantly reduce the incidence of leaf scald. Foliar application of mancozeb, also reduces the incidence and severity of the fungal disease.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

amage Caused by Locust in Rice

Importance of the problem	Oriental migratory locusts are commonly found in all rice environments but they are more concentrated in rainfed areas. The nymph and adult of the insect cause damage by consuming large amounts of leaves. Both the adults and the nymphs are nocturnal. The attack is seen mostly in dry periods. Management depends on the level of severity of infestation.
Common signs and symptoms	Feeding marks on leaves and shoots Large portions of leaf edges consumed Panicles cut-off Eggs in pods Presence of yellow and brown nymphs and adults feeding on rice foliage
Problems with similar symptoms	The symptoms can be confused with the damage caused by other insect defoliators on the rice crop.
Causal organism and their spread	Locusta migratoria manilensis Meyen Oriental migratory locusts are commonly found in all rice environments but they are more concentrated in rainfed areas. They predominate the irrigated rice environment surrounded by grassland breeding grounds. Both the adults and the nymphs are nocturnal. They feed on the rice foliage at night. At daytime, they hide at the base of the plant. Under favorable conditions, the adults swarm and migrate. Oriental migratory locust also prefers bamboo, banana, beans, betel, cassava, citrus, coconut, cotton, fibers, groundnut, kenaf, kumquat, lablab, legumes The locust is a large insect with a smooth or finely dotted integument. Its filiform antenna is about as long as the head and pronotum combined. The adults have two forms. The darker adults are those that are bred at high population densities. They have wider heads with almost concave or straight in profile low pronotal crest. They have shorter femur than its wings. The other form of adults came from low population densities. They have a narrow head, high pronotal crest, and long hind femur. Neonate nymphs of oriental migratory locust are gray-brown and measure 6 to 10 mm long. Mature nymphs exhibit two colors. At low densities, they are either green or brown. The nymphs are reddish or brownish orange at high densities. Two thin horizontal black stripes are prominent behind the compound eyes. A broader horizontal black band is also located on the lateral sides of the pronotum, on the developing wing pads, and on the dorsal and lateral surfaces of the abdomen. The eggs of both short-horned grasshopper and oriental migratory locust are in pods. They are capsule-like and yellow to dull reddish brown. With age, they turn darker.
Mechanism of damage	Oriental migratory locusts feed on the leaf margins of leaves.
Ideal management strategy	Flooding the stubbles, shaving of bunds, sweeping along the bunds and adults can be picked directly from the foliage at night because they are sluggish. Scelionid wasps parasitize the eggs of short-horned grasshopper. Nymphs and adults are hosts of parasitic flies, nematodes, and fungal pathogens. They are also infected by a certain species of an entomophthoralean fungus. Among the predators, birds, frogs, and web-spinning spiders are known. A platystomatid fly and mite prey on the eggs of oriental migratory locust. Different species of ants feed on the nymphs and adults. They are also prey to birds, bats, field rats, mice, wild pigs, dogs, millipedes, fish, amphibia, reptiles, and monkeys. A fungus also infects the insect pest. Chemical management includes the use of poison baits from salt water and rice bran. Foliar sprays can also control grass hoppers in rice fields. Granules are not effective.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Mealy Bug in Rice

Importance of the problem	Mealy bug is an important and common pest in rice fields. The insect is found in upland and rainfed environments. It occurs in great number during the rainy season. The insect feeds on rice during the tillering and stem elongation stages. The noticeable symptoms are yellowing and stunting of the crop. And when the population of mealy bug goes very high management strategy need to be adopted.
Common signs and symptoms	Hyaline to yellowish to pinkish eggs Crawlers or nymphs, unwinged pink female adults and winged pale yellow males removing plant sap Appearance of wax covering the eggs, nymphs and adults that stick on the stem or leaf Wilting Plant stunting Yellowish curled leaves Damaged spots or chakdhora or soorai disease Not uniform pattern of damage
Problems with similar symptoms	Stunting is also a damage symptom caused by other insect pests like root grubs and rice root aphids. However, presence of rice mealy bug confirms its damage on the rice plant.
Causal organism and their spread	Rice mealy bug (Brevennia rehi (Lindinger)) causes the damage. Both adult and nymph causes the damage by sucking the plant sap. The pale yellowish male adults have a single pair of wings and a waxy style-like process at the end of the abdomen. The first and middle legs of the male are approximately equal, whereas the last or third legs are longer. The body is 0.7-0.9 mm long. Adult females are oblong and wingless. They are reddish white and soft-bodied. Their body is covered with a distinct waxy or powdery coating. They measure about 1.2-3.0 mm long and 0.5-1.5 mm wide. They resemble woodlice in shape. The first instar nymphs or crawlers measure 0.1-0.2 mm wide and 0.3-0.5 mm long. Mature crawlers are 3-4 mm long. The elongated or oval eggs are hyaline to yellowish to pinkish. They are 0.3 by 0.5 mm. They are covered with wax. The eggs turn grayish red when about to hatch. Dry spells and the presence of grassy weeds (such as Echinochloa sp. and Cyperus sp) that harbor this insect pest favor the population buildup of the rice mealy bug. Likewise, well-drained soils are also suitable for the insect pest. The rice mealy bug is found in upland and rainfed environments. It is not common in irrigated rice. It occurs in great number during the rainy season. The insect is abundant in April to early July where two generations are completed during this period.
Mechanism of damage	Both the adults and nymphs remove plant sap using their sucking mouthparts.
Ideal management strategy	Apply dimethoate at 0.05% Biological control can suppress the rice mealy bugs. Small encyrtid wasps parasitize mealy bugs. Spiders, chloropid fly, drosophilid, and lady beetles are predators of the mealy bugs.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Mixed Variety

Importance of the problem	Mixed variety is a problem noticed when the crop get established. Plants with different height, maturity, color and/or grain characteristics will be seen in the field. The pattern of off type plants tends to be reasonably uniformly spread across the field. Since, seeds are the starting points in cultivation, special care need to be given to ensure the quality of seed before use.
Common signs and symptoms	Plants (off types) in field have different height, maturity, color and/or other characteristics (e.g., grain characteristics) The pattern of off types tends to be reasonably uniformly spread across the field, but may be patchy
Problems with similar symptoms	The symptoms are similar to the symptoms affected by replanting and early rat damage-causing differences in plant development.
Causal organism and their spread	The problem arises primarily as most farmers keep their own seed and do not tend to do any seed processing to ensure varietal purity or seed quality. The increase in direct seeding can also be a factor as the number of volunteer plants (i.e., those germinating from fallen seed) increase with continuous cropping and direct seeding.
Mechanism of damage	Mixed varieties differ in height and maturity leading to differences in grain filling and moisture at the time of harvest. Differences in maturity may also result in direct losses with seed being lost due to shattering. Tall plants can shade nearby plants lowering yield potential of the surrounding plants.
Ideal management strategy	Seed sources should have high viability, high germination rates, varietal purity and seed should be full (i.e., high thousand grain weight for the variety) and free of insects, diseases and weed seeds. The problem of poor seed arises as most farmers keep their own seed and do not tend to do any seed processing to ensure varietal purity or seed quality. Ensure volunteers from previous crops are not allowed to develop.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Mole Cricket in Rice

Importance of the problem	Mole cricket is an pest of rice mainly seen in nurseries. The attack normally results when flooded rice is drained. The attacked plants are cut at the base and the roots have visible feeding damage. The insect tunnels made by mole crickets appear as disturbed soil areas. Management of the insect mainly depends on the intensity of the attack.
Common signs and symptoms	presence of tan nymphs in tunnels on soil areas near the roots brown adults Loss of plant stand Seedlings cut at the base Poor seedling growth Seedling death Missing plants Root damages
Problems with similar symptoms	Loss of plant stand and the missing plants are symptoms also caused by ants
Causal organism and their spread	Mole cricket (Gryllotalpa orientalis Burmeister) causes the damage. The nymphs feed on roots and damage the crops in patches. Mole crickets occur in all rice environments. They are more common in non-flooded upland fields with moist soil. In flooded rice fields, mole crickets are usually seen swimming in the water. They are also found in permanent burrows or foraging-galleries in levees or field borders. The entrances to burrows in the soil are marked by heaps of soil. Besides rice, the insect pest feeds on Allium cepa L. (onion), Brassica oleraceae L. (cabbage), Camellia sinensis (L.) O. Ktze. (tea), Helianthus annuus L. (sunflower), Hordeum sp. (barley), Nicotiana tabacum L. (tobacco), Solanum tuberosum L. (white potato), and Triticum aestivum L. em. Thell. (wheat). The adult mole cricket is brownish and very plump. It measures 25-40 mm long. It has short antennae and its folded wings do not cover the entire length of the abdomen. The enlarged front legs, which are modified for digging, have strong teeth-like structures. Neonate nymph has a white and bluish prothorax and legs. With age, it turns gray to black with white markings. The last nymphal stage is similar to the adult except for its short wing pads. Eggs are oblong to oval and gray with a shiny surface. They are 2.6 mm long. The eggs are deposited in a hole constructed by the adult female.
Mechanism of damage	The mole cricket tunnels into the soil using its enlarged fore legs. It feeds on seeds and resulting in loss of plant stand or poor crop stands.
Ideal management strategy	Maintain standing water, which can help remove the eggs on the soil. The rice field can be flooded for 3-4 days. Levelling the field provides better water control. The eggs can also be eliminated using bund shaving and plastering of fresh wet soil. Construction of a raised nursery should be avoided to reduce feeding damage on seedlings. During land preparation, the nymphs and adults can be collected. Modern varieties with long and dense fibrous root can tolerate damage better. For natural biological control, a sphecid wasp, carabid beetle, nematodes, and a fungus are recorded as important natural enemies of the mole cricket. Mole crickets eat each other when they are together because of their cannibalistic behavior. There are poisoned baits made by mixing moistened rice bran and insecticide that can be placed along rice bunds or drier areas of the field, which can kill night-foraging mole crickets. Granular insecticides are effective unlike foliar insecticides.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Narrow Brown Leaf Spot in Rice

Importance of the problem	Narrow brown leaf spot is an important fungal disease of rice. The disease usually occurs during the late growth stages of the crop. Premature death of leaves and leaf sheaths, premature ripening of kernels and lodging of plants are symptoms observed. It causes grain discoloration and chalkiness and thereby decreases the market value. Therefore, management of the disease is very much important in rice cultivation.
Common signs and symptoms	Short, narrow, elliptical to linear brown lesions usually on leaf blades but may also occur on leaf sheaths, pedicels, and glumes or rice hulls Lesions about 2-10 mm long and 1 mm wide Lesions narrower, shorter, and darker brown on resistant varieties Lesions wider and lighter brown with gray necrotic centers on susceptible varieties Leaf necrosis may also occur on susceptible varieties Lesions occur in large numbers during the later growth stages
Problems with similar symptoms	The symptoms are similar to white leaf streak, which is caused by Mycovellosiella oryza and early stage of bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola. However, the linear form of the lesions of narrow brown leaf spot makes the disease distinct from other leaf diseases.
Causal organism and their spread	The narrow brown leaf spot is caused by a fungus (Cercospora oryzae Miyake),. The disease is observed on rice crops grown on soil deficient in potassium. Temperature ranging from 25-28° C is favorable for the optimum growth of the disease. Susceptibility of the variety to the fungus and the growth stage of the rice crop are other factors that affect the development of the disease. Although rice plants are susceptible to the fungus at all stages of growth, they are more susceptible from panicle emergence to maturity, thus, becoming more severe as rice approaches maturity. Aside from the rice plant, the fungus can survive on Panicum maximum Jacq. (guinea grass), P. repens L. (torpedo grass), and Pennisetum purpureum K. Schum. (elephant grass).
Mechanism of damage	The fungus penetrates the host tissue through the stomata. It becomes stable in the parenchyma where it stays beneath the stomata and spreads longitudinally in the epidermal cells.
Ideal management strategy	Cultural practices, such as the use of potassium and phosphorus fertilizers, and planting of early maturing cultivars early in the growing season, are recommended to manage the narrow brown leaf spot. The use of resistant varieties is the most effective approach to manage the disease.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Nitrogen Deficiency Disorder in Rice

Importance of the problem	Nitrogen deficiency is one of the most common problems in rice. Nitrogen is an essential constituent of amino acids, nucleic acids, nucleotides, and chlorophyll. Deficiency of nitrogen reduces growth and grain production. The plant needs more nitrogen during the tillering and panicle initiation stages. Hence, application of nitrogen in right amount and time is very much important in rice cultivation.
Common signs and symptoms	Leaves become narrow, short, erect, and lemon-yellowish green except for young leaves, which may remain greener Nitrogen is very mobile within the plant and, because nitrogen is translocated from old senescent leaves to younger leaves, deficiency symptoms tend to occur initially in older leaves. Sometimes all leaves become light green and chlorotic at the tip Entire field may appear yellowish Leaves die under severe nitrogen stress Reduced tillering stunted growth, reduction in grain number.
Problems with similar symptoms	The visual symptoms of N deficiency can be confused with those of S deficiency, but S deficiency is less common and tends to first affect younger leaves or all leaves on the plant. Mild N deficiency can be confused with Fe deficiency, but the latter affects the emerging leaf first.
Causal organism and their spread	Deficiency of nitrogen especially during the tillering and panicle initiation stage causes the problem. Nitrogen deficiency results out of: • Low soil N-supplying power. • Insufficient application of mineral N fertilizer. • Low N fertilizer use efficiency (losses from volatilization, denitrification, incorrect timing and placement, leaching, and runoff). • Permanently submerged conditions that reduce indigenous soil N supply (i.e., in triple cropping systems). • N loss caused by heavy rainfall (leaching and seepage). • Temporary drying out of the soil during the growing period. • Poor biological N2 fixation because of severe P deficiency.
Mechanism of damage	N is an essential constituent of amino acids, nucleic acids, nucleotides, and chlorophyll. It promotes rapid growth (increased plant height and tiller number) and increased leaf size, spikelet number per panicle, percentage filled spikelets in each panicle, and grain protein content. Thus, N affects all parameters contributing to yield. Leaf N concentration is closely related to leaf photosynthesis rate and crop biomass production. N drives the demand for other macronutrients such as P and K. NO3-N and NH4-N are the major sources of inorganic N uptake. Most absorbed NH4-N is incorporated into organic compounds in roots, whereas NO3-N is more mobile in the xylem and is also stored in the vacuoles of different plant parts. NO3-N may also contribute to maintaining the cation-anion balance and osmoregulation. To fulfill essential functions as a plant nutrient, NO3-N must be reduced to ammonia through the action of nitrate and nitrite reductases.
Ideal management strategy	Do not apply large amounts of N to less responsive varieties, e.g., traditional (tall) varieties with low harvest index grown in rainfed lowland and upland environments. Choose suitable plant spacing for each cultivar. Crops with suboptimal plant densities do not use fertilizer N efficiently. Maintain proper water control, i.e., keep the field flooded to prevent de-nitrification but avoid N losses from water runoff over bunds immediately following fertilizer application. Optimal response to N fertilizer depends on proper overall crop management. Establish a dense, healthy rice crop by using high-quality seed of a high-yielding variety with multiple pest resistance and a suitable plant density. Control weeds that compete with rice for N. Control insects and diseases (damage reduces canopy efficiency and thus rice productivity). At the end of the rice season, losses of residual soil NO3-N can be reduced if a dry-season crop is planted to recover residual N or if weeds are allowed to develop and then are incorporated into the soil in the subsequent cropping cycle. Correct deficiencies of other nutrients (P, K, and Zn) and solve other soil problems (shallow rooting depth, toxicities). Response to applied N will be small on acid, low-fertility rainfed lowland and upland soils unless all existing soil fertility problems (acidity, Al toxicity, deficiencies of P, Mg, K, and other nutrients) have been corrected. Apply available organic materials (farmyard manure, crop residues, compost) on soils containing a small amount of organic matter, particularly in rainfed lowland rice and intensive irrigated rice systems where rice is rotated with other upland crops such as wheat or maize. In irrigated rice-rice systems, carry out dry, shallow tillage (5-10 cm) within 2 wk of harvest. Early tillage enhances soil oxidation and crop residue decomposition during fallow and increases N availability up to the vegetative growth phase of the succeeding rice crop. Increase the indigenous N-supplying power of permanently submerged soils by periodic drainage and drying. Examples are a midseason drainage of 5-7 d at the late tillering stage (about 35 d after planting) or occasional thorough aeration of the soil by substituting upland crop for one rice crop, or omitting one rice crop. Application of N fertilizer is standard practice in most rice systems. To achieve yields of 5-7 t ha-1, fertilizer N rates typically range from 80 to 150 kg ha-1. • N fertilizer should be applied when the crop has the greatest need for N and when the rate of uptake is large. The highest recovery efficiency of applied N is achieved during late tillering to heading stages. Use NH4 fertilizers as an N source for top dressed N applications. Apply a late N dose (at flowering) to delay leaf senescence and enhance grain filling, but only to healthy crops with good yield potential. Use other means of increasing N use efficiency if they are economically viable. Examples include: N fertilizer placement in the reduced soil layer about 8-10 cm below the soil surface (deep placement of urea supergranules, tablets, briquettes, mudballs), and Slow-release N fertilizer (S-coated urea) or poly-olefin coated urea incorporated as a basal dressing before planting.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Excess Nitrogen in Rice

Importance of the problem	Nitrogen fertilizers are increasingly used by farmers to produce a heavy yield. But at times, the amount of nitrogenous fertilizers applied, can go higher than recommended dosage. This results in increased disease and pest incidences and many other growth deformities. Therefore, a cautious effort in this direction is very much essential in rice cultivation.
Common signs and symptoms	Plants look overly green Growth distributed in patches. Some areas will show more growth over other areas. (This happens mainly due to uneven application across the field) May be healthy, but also may be lodged at maturity (especially in direct-seeded rice) May have thin stems May have increased disease (e.g., bacterial leaf blight, sheath blight, blast) or insects (leaf folder)
Problems with similar symptoms	P deficiency will produce dark green leaves that may be confused with excessive N application; however P deficient plants produce fewer tillers and have stunted growth.
Causal organism and their spread	Excess nitrogen is typically used where fertilizers are relatively cheap and where farmers don’t understand the amount of nitrogen required relative to their yield goals and the right time of N application.
Mechanism of damage	Excessive N or unbalanced fertilizer application (large amounts of N in combination with small amounts of P, K, or other nutrients) may reduce yield because of one or more of the following: • Mutual leaf shading caused by excessive vegetative growth. • Increased number of unproductive tillers that shade productive tillers and reduce grain production. • Lodging caused by the production of long, weak stems. • Increased number of unfilled grains. • Reduced milling recovery and poor grain quality. • Increased incidence of diseases such as bacterial leaf blight (caused by Xanthomonas oryzae), sheath blight (caused by Rhizoctonia solani), sheath rot (caused by Sarocladium oryzae), stem rot (caused by Helminthosporium sigmoideum), and blast (caused by Pyricularia oryzae) because of greater leaf growth and dense crop stand. • Increased incidence of insect pests, particularly leaffolder, Cnaphalocrocis medinalis.
Ideal management strategy	Farmers should apply sufficient N to meet the plants needs. On average this equates to around 20 kg N for each t of grain produced. The farmer needs to know how much N is coming from the soil and other sources (e.g., water or bacteria in the soil or water) and then apply the additional N to meet the yield goal. The Leaf color chart is a simple tool ensuring that sufficient but not excessive N is applied. It helps farmers to determine the right time of N application based on crop need and soil N supply
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Phosphorous Deficiency Disorder in Rice

Importance of the problem	Phospherous play the critical role in tillering, root development, early flowering, and ripening. Its major functions are in energy storage and transfer and membrane integrity. It is particularly important in early growth stages. The addition of mineral phosphatic fertilizer is required when the rice plant’s root system is not yet fully developed and the native soil phospherous supply is small.
Common signs and symptoms	• Leaves, particularly older ones, are narrow, short, very erect, and "dirty" dark green • Young leaves appear to be healthy but older leaves turn brown and die • Red and purple colors may develop in leaves if the variety has a tendency to produce anthocyanin • Leaves appear pale green when P and N deficiency occur simultaneously • Stems are thin and spindly and plant development is retarded (Stunted plants) • The number of leaves, tillers, panicles, and grains per panicle get reduced • Delayed maturity (often by 1 week or more). When P deficiency is severe, plants may not flower at all. • Large proportion of empty grains. When P deficiency is very severe, grain formation may not occur. • Low 1,000-grain weight and poor grain quality. • No response to mineral N fertilizer application. • Low tolerance for cold water. • Absence of algae in floodwater. • Poor growth (small leaves, slow establishment) of green manure crops.
Problems with similar symptoms	P deficiency will produce dark green leaves that may be confused with excessive N application; however P deficient plants produce fewer tillers and have stunted growth. P deficiency is often associated with other nutrient disorders such as Fe toxicity at low pH, Zn deficiency, Fe deficiency, and salinity in alkaline soils.
Causal organism and their spread	Deficiency of phosperous especially during the initial stages of growth causes the problem. Phosperous deficiency results out of: • Insufficient application of mineral P fertilizer. • Low indigenous soil P-supplying power. • Low efficiency of applied P fertilizer use due to high P-fixation capacity or erosion losses (in upland rice fields only). • P immobilization in Ca phosphates due to excessive liming. • Excessive use of N fertilizer with insufficient P application. • Crop establishment method (P deficiency is more likely in direct-seeded rice due to high plant densities and shallow root systems).
Mechanism of damage	Phosphorus is an essential constituent of adenosine triphosphate (ATP), nucleotides, nucleic acids, and phospholipids. Its major functions are in energy storage and transfer and membrane integrity. It is mobile within the plant and promotes tillering, root development, early flowering, and ripening (especially where the temperature is low). It is particularly important in early growth stages. The addition of mineral P fertilizer is required when the rice plant’s root system is not yet fully developed and the native soil P supply is small. P is remobilized within the plant during later growth stages if sufficient P has been absorbed during early growth.
Ideal management strategy	• In rice-rice systems, carry out dry, shallow tillage (10 cm) within 2 weeks after harvest. Early tillage enhances soil oxidation and crop residue decomposition during the fallow period and increases P availability during vegetative growth of the succeeding rice crop. • On acid, low-fertility rainfed lowland and upland soils, all existing soil fertility problems (acidity, Al toxicity, and deficiencies of Mg, K, and other nutrients) must be corrected before a response to P is obtained. • In field trials with irrigated rice in southern India, an increase in P availability was found after the application of phosphobacteria to the soil, as seed coating, or as seedling dip. • Establish a healthy plant population by using high-quality seed of a high-yielding variety with multiple pest resistance planted at the correct density with proper water and pest management. • Incorporate rice straw. Although the total amount of P recycled with the straw is small (1 kg P t-1 straw), it will contribute to maintaining a positive P balance in the long term. • To maintain yields of 5-7 t ha-1 and replenish P removed with grain and straw, fertilizer P rates should be in the range of 15 to 30 kg P ha-1. • In upland rice systems, P fixation can be reduced by applying P fertilizer in a band beneath the seed. Root proliferation in and close to the band increases with increased soluble-P concentration near the root surface. • Rock phosphate should be broadcast and incorporated before flooding when soil pH is low to allow reactions between the soil and fertilizer that release P for plant uptake.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Poor Quality Seed in Rice

Importance of the problem	Poor seed quality is a problem commonly faced by most of the farmers. The problem arises primarily as most farmers keep their own seed and do not tend to do any seed processing to ensure varietal purity or seed quality. Since, seeds are the starting points in cultivation, special care need to be given to ensure the quality of seed before use.
Common signs and symptoms	• Low germination, mixed varieties, low plant vigor, diseased plants or the introduction of weeds • Seed source may be discolored • Seeds may be of different sizes and varieties • Seed sources may contain inert, weeds or other matter • Pattern of damage is usually general across the field
Problems with similar symptoms	Various problems causing problems of crop establishment (e.g., cloddy soil, seed too deep, soil too soft at seeding, poor emergence in low spots in fields, heavy rainfall at seeding, soil crusting, poor seed distribution, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting.
Causal organism and their spread	The problem arises as most farmers keep their own seed and do not tend to do any seed processing to ensure varietal purity or seed quality.
Mechanism of damage	Poor seed results in lost yield due to a variety of reasons including: low seedling vigor and poor growth, mixed varieties differing in height and maturity, the introduction of weeds, insects and diseases.
Ideal management strategy	Seed sources should have high viability, high germination rates, seed should be full (high thousand grain weight for the variety) and free of insects, diseases and weed seeds. The problem of poor seed arises as most farmers keep their own seed and do not tend to do any seed processing to ensure varietal purity or seed quality.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Poor Seed Distribution in Rice

Importance of the problem	Good seed distribution is very much important in rice cultivation. A well distributed seeds will provide ample space for the crop to grow. The absence of a good stand automatically lowers yield potential. Therefore, ensuring proper distribution of seeds is very much important. And the problem is very much serious in areas where labour is the limiting factor.
Common signs and symptoms	Inadequate or uneven plant stand (e.g., plants too far apart or missing)
Problems with similar symptoms	This should not be confused with factors affecting crop stand (e.g., low seed rate, or mixed variety), pest damage during establishment (e.g., rats, birds, snails or possibly crabs).
Causal organism and their spread	Poor seed distribution is typically a problem where labor supplies are becoming limited.
Mechanism of damage	Yield potential can be lost directly and/or greater weed pressure can result from the lack of crop-weed competition. If a low seed rate results in a low crop stand, then groundcover can be low. Thus yield potential can be lost directly and/or indirectly due to greater weed pressure resulting from the lack of crop-weed competition.
Ideal management strategy	• If labor supplies are inadequate, then a shift to mechanized transplanting or direct seeding may be required. Both of these crop establishment options requires that fields have good water management and are well leveled. • Ensure an appropriate seed rate with even distribution of seed. • In direct seeded fields, the target number of spikes varies with season and variety but typically ranges from 350 to over 500 spikes per m2. • A direct seeded plant will typically give of the order of 2-3 spikes per plants. Thus, crop stand should be of the order of 100 to 200 plants per m2. • Seed rates between 40 to 100 kg per ha are usually sufficient, if other factors (e.g., pest problems and seedbed preparation) are not problematic.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Poor Transplantation

Importance of the problem	The basic purpose of transplantation is to establish plants at ideal spacing and in good condition. A good plant stand lays the foundation for good yields. However, because of variety of problems like labour, rain, weed etc transplanted fields shows gaps and uneven growth. Such defective practices greatly affects yield and need to be controlled through proper management.
Common signs and symptoms	• Inadequate or uneven plant stand (e.g., plants too far apart or missing) • Variable pattern of this problem in the field
Problems with similar symptoms	This should not be confused with factors affecting crop stand (e.g., low seed rate, or poor seed distribution), pest damage during establishment (e.g., rats, birds, snails or possibly crabs).
Causal organism and their spread	Poor transplanting is typically a problem where labor supplies are becoming limited.
Mechanism of damage	Yield potential can be lost directly and/or greater weed pressure can result from the lack of crop-weed competition. If a low seed rate results in a low crop stand, then groundcover can be low. Thus yield potential can be lost directly and/or indirectly due to greater weed pressure resulting from the lack of crop-weed competition.
Ideal management strategy	If labor supplies are inadequate, then a shift to mechanized transplanting or direct seeding may be required. Both of these crop establishment options requires that fields have good water management and are well leveled. Ensure an appropriate seed rate with even distribution of seed. In direct seeded fields, the target number of spikes varies with season and variety but typically ranges from 350 to over 500 spikes per m². A direct seeded plant will typically give of the order of 2-3 spikes per plants. Thus, crop stand should be of the order of 100 to 200 plants per m². Seed rates between 40 to 100 kg per ha are usually sufficient, if other factors (e.g., pest problems and seedbed preparation) are not problematic.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Potassium Deficiency Disorder in Rice

Importance of the problem	Potassium provides strength to plant cell walls and increases leaf area and leaf chlorophyll content. It improves the rice plant’s tolerance of adverse climatic conditions, lodging, insect pests, and diseases. Potassium increases the number of spikelets per panicle, percentage of filled grains, and 1,000-grain weight. Hence, application of potassium fertilizer is very much important in rice cultivation.
Common signs and symptoms	• Dark green plants with yellowish brown leaf margins or dark brown necrotic spots appearing first on the tip of older leaves • Leaf tips yellowish brown under severe K deficiency • Symptoms appear first on older leaves, then along the leaf edge, and finally on the leaf base • Affected plants with upper leaves short, droopy, and "dirty" dark green • Older leaves change from yellow to brown • Discoloration gradually appears on younger leaves if deficiency is not corrected • Leaf tips and margins may dry up • Yellow stripes may appear along leaf interveins and lower leaves may bend downward • General pattern of damage is patchy within a field, affecting single hills rather than the whole field • Rusty brown spots on tips of older leaves and later spread over the whole leaf causing it to turn brown and dry if K deficiency is severe • Irregular necrotic spots may also occur on panicles. • Stunted plants with smaller leaves, short and thin stems • Tillering is only reduced under very severe deficiency • Greater incidence of lodging. • Early leaf senescence, leaf wilting, and leaf rolling when temperature is high and humidity is low. • Large percentage of sterile or unfilled spikelets caused by poor pollen viability and retarded carbohydrate translocation. Reduced 1,000-grain weight. • Unhealthy root system (many black roots, reduced root length and density), causing a reduction in the uptake of other nutrients. Reduced cytokinin production in roots.
Problems with similar symptoms	Leaf symptoms of potassium deficiency, particularly the yellowish brown leaf margins, are similar to those of tungro virus disease. Unlike potassium deficiency, tungro occurs as patches within a field, affecting single hills rather than the whole field.
Causal organism and their spread	Deficiency of potassium at all stages of growth causes the problem. Potassium deficiency results out of: • Low soil K-supplying capacity. • Insufficient application of mineral K fertilizer. • Complete removal of straw. • Small inputs of K by irrigation (irrigation water low in K). • Low recovery efficiency of applied K fertilizer because of high K-fixation capacity or leaching losses. • Presence of excessive amounts of reduced substances in poorly drained soils (e.g., H2S, organic acids, Fe2+), resulting in retarded root growth and reduced K uptake. • Wide Na:K, Mg:K, or Ca:K ratios in soil, under sodic/saline conditions. Excess Mg in soils derived from ultrabasic rocks. Bicarbonate is high in irrigation water.
Mechanism of damage	Potassium has essential functions in osmoregulation, enzyme activation; regulation of cellular pH, the cation-anion balance, regulation of transpiration by stomata, and the transport of assimilates (the products of photosynthesis). K provides strength to plant cell walls and is involved in the lignification of sclerenchyma—tissues with thickened cell walls. On the whole-plant level, K increases leaf area and leaf chlorophyll content, delays leaf senescence, and therefore contributes to greater canopy photosynthesis and crop growth. Unlike N and P, K does not have a pronounced effect on tillering. K increases the number of spikelets per panicle, percentage of filled grains, and 1,000-grain weight. K deficiency results in an accumulation of labile low-molecular-weight sugars, amino acids, and amines that are suitable food sources for leaf disease pathogens. K improves the rice plant’s tolerance of adverse climatic conditions, lodging, insect pests, and diseases. Deficiency symptoms tend to occur in older leaves first, because K is very mobile within the plant and is re-translocated to young leaves from old senescing leaves. Often, yield response to K fertilizer is only observed when the supply of other nutrients, especially N and P, is sufficient. Poor root oxidation power, causing decreased resistance to toxic substances produced under anaerobic soil conditions, e.g., Fe toxicity caused by K deficiency. Increased incidence of diseases, particularly brown leaf spot (caused by Helminthosporium oryzae), cercospora leaf spot (caused by Cercospora spp.), bacterial leaf blight (caused by Xanthomonas oryzae), sheath blight (caused by Rhizoctonia solani), sheath rot (caused by Sarocladium oryzae), stem rot (caused by Helminthosporium sigmoideum), and blast (caused by Pyricularia oryzae) where excessive N fertilizer and insufficient K fertilizer have been used.
Ideal management strategy	• Increase K uptake by improving soil management practices on root health (e.g., deep tillage to improve percolation to at least 3-5 mm d-1 and to avoid excessively reducing conditions in soil). • Establish an adequate population of healthy rice plants by using high-quality seed of a modern variety with multiple pest resistance, and optimum crop maintenance (water and pest management). • Incorporate rice straw. If straw burning is the only option for crop residue management, spread the straw evenly over the field (e.g., as it is left after combine harvest) before burning. Ash from burnt straw heaps should also be spread over the field. • Apply optimum doses of N and P fertilizers and correct micronutrient deficiencies. Apply K fertilizers, farmyard manure, or other materials (rice husk, ash, night soil, compost) to replenish K removed in harvested crop products • Correct deficiencies of other nutrients (N, P, Zn), correct other soil problems (restricted rooting depth, mineral toxicities), and ensure proper overall crop management to maximize the response to K fertilizer. • To maintain yields of 5-7 t ha-1 and replenish K removed with grain and straw, fertilizer K rates may range from 20 to 100 kg K ha-1.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Blast Disease in Rice

Importance of the problem	Rice blast is one of the most destructive diseases of rice. The disease infects the rice plant at any growth stage. Rice seedlings or plants at the tillering stage are often completely killed. Likewise, heavy infections on the panicles usually cause a loss in rice yields. Therefore, management of rice blast at the initial stages of infection is very much important.
Common signs and symptoms	Initial symptoms are white to gray-green lesions or spots with darker borders produced on all parts of shoot Older lesions elliptical or spindle-shaped and whitish to gray with necrotic borders Lesions wide in the center and pointed toward either end Lesions may enlarge and coalesce to kill the entire leaves Larger lesions (2 cm long) at reproductive stage on younger plants (< 1 cm long) Symptoms also observed on leaf collar, culm, culm nodes, and the panicle neck node Internodal infection of the culm occurs in a banded pattern with a 3-cm blackened necrotic culm and 3-cm healthy tissue in succession Nodal infection causes the culm to break at the infected node Few, no seeds, or whiteheads when neck is infected or rotten
Problems with similar symptoms	The pinhead-size brown lesions can be confused from the symptoms of brown spot disease caused by Helminthosporium oryzae. However, in blast the lesions are elongated and pointed at each end. The whiteheads symptom looks the same as the whiteheads produced by the stem borer.
Causal organism and their spread	A fungus Pyricularia oryzae Cavara (anamorph), causes rice blast. The blast spores are present in the air throughout the year. The infection brought about by the fungus damages upland rice severely than the irrigated rice. It rarely attacks the leaf sheaths. Primary infection starts where seed is sown densely in seedling boxes for mechanical transplanting. Growing rice in aerobic soil in wetlands where drought stress is prevalent also favors infection. Cloudy skies, frequent rain, and drizzles favor the development and severity of rice blast. High nitrogen levels, high relative humidity, and wet leaves encourage infection caused by the fungus. The rate of sporulation is highest with increasing relative humidity of 90% or higher. For leaf wetness, the optimum temperature for germination of the pathogen is 25-28 °C.
Mechanism of damage	Conidia are produced on lesions on the rice plant about 6 days after inoculation. The production of spores increases with increase in the relative humidity. Most of the spores are produced and released during the night. After spore germination, infection follows. Infection tubes are formed from the appressoria and later the penetration through the cuticle and epidermis. After entering the cell, the infection tube forms a vesicle to give rise to hyphae. In the cell, the hyphae grew freely.
Ideal management strategy	Early sowing of seeds after the onset of the rainy season is more advisable than late-sown crops. Excessive use of fertilizer should be avoided as it increases the incidence of blast. Nitrogen should be applied in small increments at any time. Water management practices in rainfed areas lessen the likelihood of stress, which also aid in blast control. Planting resistant varieties against the rice blast is the most practical and economical way of controlling rice blast. Systemic fungicides such as Carbendazim and Tricyclazole can be used for seed treatment. For spraying Carpropamid, Kitazin, Carbendazim can be used.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Rice Bug Attack in Paddy Fields

Importance of the problem	The rice bug is an important insect pest during the milky stage of the rice plant. Both the nymphs and adults prefer the endosperm of the rice grain resulting to production of smaller grains. They also feed during the soft or dough stages and can cause grain discoloration. Both the adults and nymphs feed on grains at the milking stage. They can be serious pests of rice and sometimes reduce yield by as much as 30%.
Common signs and symptoms	• Some grains or ear heads appear chaffy. • Bugs seen flying about when disturbed with buggy odour. • oval, shiny, and reddish brown eggs along midrib of leaf • slender and brown-green nymphs and adults feeding on endosperm of rice grains • feeding causes empty or small grains during the milking stage • feeding causes deformed or spotty grains at the soft or hard dough stage • grains become dark • Erect panicles • Deformed or spotty grains
Problems with similar symptoms	The symptoms can be confused with the damage caused by nutrient deficiency or flower thrips.
Causal organism and their spread	Gandhi bug (Leptocorisa acuta) causes the damage. The adults of the three species of rice bugs are slender and brown-green. They measure 19-16 mm long. They have long legs and antennae. Distinct ventrolateral spots on the abdomen are either present or absent. The female bug lays eggs on the leaves in rows. Eggs are reddish brown in colour.The younger instars are pale in color. The nymphs have long antennae. The older instars measure 1.8-6.2 mm long. They are yellowish green. Conditions favorable for the spread of the pest are • staggered rice planting • woodlands and extensive weedy areas near rice fields • wild grasses near canals • warm weather, overcast skies, and frequent drizzles • rainfed and wetland or upland rice • flowering to milky stages of the rice plant
Mechanism of damage	Both adults and nymphs insert their needlelike mouthparts between the lemma and palea of the rice hull to suck the endosperm of rice grain. In order to feed, they secrete a liquid to form a stylet sheath that hardened around the point of feeding and holds the mouthparts in place.
Ideal management strategy	Removal of alternate hosts such as grasses on bunds, early planting, and the use of late-maturing cultivars. Netting and handpicking the bugs reduce their numbers. Likewise, putting attractants such as arasan or anything with an odor like dead snails or rats can easily capture rice bugs in the field. Among the biological control agents, small wasps parasitize the eggs and the meadow grasshoppers prey on them. Both the adults and nymphs are preys to spiders, coccinellid beetles and dragonflies. A fungus infects both nymphs and adults. Coarse-grain and bearded cultivars may be resistant to the rice bugs. When the bug is seen in large numbers apply one of the following insecticides: Malathion, phosalone, Phenthoate, methyl parathion.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Case Worm

Importance of the problem	The rice caseworm is an important defoliating pest of rice. The pest feeds on rice during the seedling and tillering stages of the crop. The damage causes skeletonized leaf tissues that usually appear ladder-like. A rice field with standing water increases the pest’s abundance. The rice plants can recover from the damage if there are no other defoliators. Otherwise, careful management strategy need to adopt.
Common signs and symptoms	• pale yellow, disc-like eggs on underside of leaves • young pale green larvae feeding on the surface of tender leaves • older larvae are enclosed within the case and feed by scraping leaf tissues or biting through leaf sheaths • The presence of leaf cases attached onto leaf sheaths and floating in the water with the larvae enclosed • Leaves cut at right angles as with a pair of scissors • Leaves with papery upper epidermis that were fed on • Skeletonized leaf tissues usually appear ladder-like • Leaf cases floating on water • cutting off leaf tips to make leaf cases • ladder-like appearance of skeletonized leaf tissues • maturity may be delayed for 7-10 days
Problems with similar symptoms	The damage symptoms can easily be confused with symptoms of other defoliating insect pests.
Causal organism and their spread	Nymphula depunctalis commonly called rice caseworm causes the damage. The adult moth is about 5 mm long. It is bright white with light brown and black spots. Individual egg is circular, flattened, and measures 0.5 mm in diameter. It is light yellow and has a smooth surface. Mature eggs are darker and develop two purplish dots. First instar larva is pale cream with light yellow head. It is 1.2 mm long. With age, the larva turns greenish. It has branched and thread-like gills along the sides of the body. The pupa is cream in color and about 5.5 mm long. Mature pupa is silvery white. The adults are nocturnal and are attracted to light traps. The larva hides in its case then float on the water surface during the day and crawls to the rice plant with its case to feed.
Mechanism of damage	The larva scrapes the green tissue of the leaf with only the white epidermis remaining. The white epidermis appears ladder-like because of the back and forth motions of the larval head during feeding.
Ideal management strategy	There are cultural control practices, which are available for the pest. For example, the use of correct fertilizer application, wider spacing (30 × 20 mm), and early planting. Furthermore, draining the field, transplanting older seedlings, or growing a ratoon can also help control this insect. Sparse planting also reduces damage. Among the biological agents, snails are useful predators of eggs of the rice caseworm. The larvae are fed upon by the hydrophilid and dytiscid water beetles. Spiders, dragonflies, and birds eat the adults. There is a nuclear polyhedrosis virus, which is a potential control agent against the rice caseworm. Rice caseworm larvae are highly sensitive to insecticides. The use of foliar treatments of carbamate insecticides can control the insect pest. Pyrethroids should be avoided as they can cause secondary problems, such as brown planthoppers. If infestation is severe, apply carbaryl dust or spray. Drainage of water from the field when the damage is severe for three days. Application of kerosine ( 1 liter) mixed with saw dust (25 Kg)
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Field Rats

Importance of the problem	Rice field rats are very much common in our fields. They feed on seeds directly. They pull up germinating seeds. They either cut or pull up transplanted plants. Tillers are usually cut and then chewed. Effective management of rodents will involve strategic actions that limit population growth so that damage is kept below the threshold of economic concern of farmers.
Common signs and symptoms	Missing germinating seeds Missing hills Chopped young seedlings Missing plants Irregular cuttings of stem Chewed developing buds on ripening grains Tillers cut near base at 45° angle Re-tillering of stems Delayed grain maturity Missing grains Missing panicles runways, active burrows and footprints are visible in the muddy areas near the damage
Problems with similar symptoms	The feeding damage on the stem caused by the rice field rats may resemble insect damage although rat damage is usually distinguished by the clean cut at 45° of the tiller. The damage on the grains is similar to bird damage.
Causal organism and their spread	Rattus argentiventer Robinson and Kloss, R. exulans Peale, R. rattus spp., R. tanezumi Rice field rats are black to brown in color. They have scaly, thinly furred tails and distinctive chisel-like incisors. The rice field rat, R. argentiventer, is the major rodent pest in SE Asia and is distinguished by a tuft of red hair at the base of its ears, fur on back orange-brown flecked with black, and a silvery white ventrum. In lowland irrigated rice crops both the wet and dry seasons are favorable for rat reproduction and crop damage. In rainfed rice crops rodents have their greatest impact in the wet season. The availability of food, water, and shelter are factors, which provide optimum breeding conditions. The presence of grassy weeds also triggers their development. Rice field rats feed at night with high activity at dusk and dawn. At daytime, they are found among vegetation, weeds, or maturing fields. During fallow period, they utilize major channels and village gardens as prime habitats. At tillering, 75% of time they are in burrows along the banks and after maximum tillering, 65% of time they are in rice paddies. Aside from the rice plant, rice field rats also feed on grasses and invertebrates living in and around the rice field.
Mechanism of damage	The breeding season of the rice field rats and their relative amount of damage are closely linked to the crop growth and development. If there is one crop per year then there is one breeding season. If there are two rice crops per year then there are two breeding seasons. Where harvest is staggered by more than one or two weeks within a single cropping area, the rat population will move from field to field, causing increasingly severe damage in the later-harvested crops. Even more critically, rats born during the early part of the cropping season will themselves be old enough to start breeding. This can produce a sudden explosion in the rat population, with densities peaking at many thousands of animals per hectare.
Ideal management strategy	Once rodent numbers are high the management actions would have to remove at least 70% of the population to have a marked effect on reduction in yield loss to rice crops. Strategic actions for management are most effective if they are developed on the basis of a sound knowledge of the ecology of the species to be controlled. To catch rats to identify the species, traps are best placed along runways, or the rats can be dug from their burrows. Other methods of physical control includes hunting, rat drives, digging, and exclusion. Cultural management actions such as hygiene around villages, keeping the cover low along the banks of main irrigation canals, maintaining smaller bunds or banks with height and width of less than 300 mm to prevent rats from utilizing these as nesting sites, synchrony of cropping, and rat campaigns at key times are recommended at the community level. Other actions include shortening the harvest period and having a 1 to 2 month fallow over the dry season. Lethal control can be implemented through the use of rodenticides like acute poisons (e.g. Zinc phosphide), chronic poisons or anti-coagulants. Among the biological control, wildcats, snakes, and birds are also predators of rice field rats.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Gall Midge Attack in Rice

Importance of the problem	The gall midge is an important and common pest of rice. The attack take place from seedbed to maximum tillering stages. As a result of the attack tubular galls and silver shoots are formed. Reddish larvae and pupae can be dissected from the base of infected tillers. And when the infected tillers are more than one in a meter, management strategy need to be adopted.
Common signs and symptoms	Formation of a hollow cavity or tubular gall at the base of the infested tiller Gall is a silvery white hollow tube, 1 cm wide and 10-30 cm long Affected tiller inhibits growth of leaves and fails to produce panicles Deformed, wilted, and rolled leaf Elongation of leaf sheaths called onion leaf or silver shoot Plant stunting
Problems with similar symptoms	The plant stunting and leaf deformity, wilting and rolling are also symptoms observed on plants caused by drought, potassium deficiency, salinity, and ragged stunt virus, orange leaf virus and tungro virus diseases. The rolled leaves can also be associated with the symptom caused by rice thrips.
Causal organism and their spread	Rice gall midge (Orseolia oryzae (Wood-Mason)) causes the damage. The rice gall midge is found in irrigated or rainfed wetland environments during the tillering stage of the rice crop. It is also common in upland and deepwater rice. During the dry season, the insect remains dormant in the pupal stage. They become active again when the buds start growing after the rains. The population density of the rice gall midge is favored mainly by cloudy or rainy weather, cultivation of high-tillering varieties, intensive management practices, and low parasitization. Wild rices, such as Oryza rufipogon are common alternate hosts.
Mechanism of damage	The larva of the gall midge moves between the sheath and the stem to reach the growing point. It feeds inside the developing buds of a new tiller and release chemicals in its saliva causing the plant to grow abnormally to produce a hollow cavity or gall at the base of the tiller. The developing and feeding larva causes the gall to enlarge and elongate at the base. Gall appears within a week after larval entry. The infected tiller becomes abnormal and silvery in color. Examination of the tubular gall shows that it is capped by a solid plug of plant tissue at the base of the point where the leaf forms.
Ideal management strategy	Use tolerant varieties like Pavithra, Panchami and Uma Avoid late transplantation during the first crop season. Careful monitoring of the crop seasons in the month of July during additional crop season and October during puncha season. Use optimum seed rate of 100 kg/ha Destruction of collateral host like wild rice Cynodon dactylon, Ischaemum aristatum, Echinochloa spp. and Isachne sp. Dipping germinated seed in 0.2% chlorpyrifos solution for 12 hours before sowing give protection up to 30 days. In transplanted crop the root of seedlings may be dipped in 0.02% chlorpyrifos suspension for 12 hours prior to planting. The nursery treatment has to be followed by main field treatment, 10-15 days after transplantation using anyone of the following insecticides: quinalphos, carbaryl, carbofuran. In areas where the pest is of regular occurrence, apply granules of carbofuran 3G (0.5 kg ai/ha), quinalphos (1.5 kg ai/ha) or chlorpyrifos 10G (0.5 kg ai/ha) within 10 days after sowing. The granules should be broadcast in 2-3 cm of water and the field should be impounded for at least 4 days. Natural biological control agents such as platygasterid, eupelmid, and pteromalid wasps, which parasitize the larvae, is effective. The pupa is host to two species of eupelmid wasps. Phytoseiid mites feed upon the eggs, whereas spiders eat the adults. Plowing ratoon of the previous crop and removing all off-season plant hosts can reduce infestation. The adults are nocturnal and they are easily collected using light traps.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage by Rice Grassy Stunt Virus

Importance of the problem	Rice grassy stunt is a virus disease that is gaining important in recent days. The disease affects mostly at the tillering stage of the rice crop. Diseased hills are severely stunted with excessive tillering and a grassy or rosette appearance. Management of the disease is very difficult as no control measure for virus is effective.
Common signs and symptoms	Diseased hills are severely stunted with excessive tillering and a very upright growth habit Diseased hills has a grassy and rosette appearance Leaves short, narrow, and yellowish green with numerous small rusty spots or patches, which form blotches Retention of green coloration of the leaves after application of sufficient nitrogenous fertilizers Infected plants usually survive until maturity, but produce no panicles The symptom develops 10-20 days after infection
Problems with similar symptoms	Stunting and increased tillering symptoms can be confused with the rice yellow dwarf and rice dwarf disease.
Causal organism and their spread	The grassy stunt virus is transmitted by the brown planthopper Nilaparvata lugens Stal. The disease can also be transmitted by Nilaparvata bakeri Muir and N. muiri China. The interaction between the virus and its vector is persistent without transovarial passage. The insect acquires the virus during at least 30 minutes of feeding period. The plants can be infected in as little as 9 minutes of feeding. Incubation in the insect takes around 5-28 days with an average of 11 days, whereas in plants, incubation ranges from 10 to 19 days. Viruliferous insects remain infective for life. Rice grassy stunt virus (RGSV) is a member of the Tenuiviruses. It has fine filamentous particles, which are 6-8 nm in diameter. It has a nodal contour length of 950-1,350 nm. The particles have one capsid protein and the genome is made up of four single-stranded RNA. The virus exists in the vector and in the rice crop. Brown plant hopper nymphs and adults transmit it where rice is grown year-round. RGSV is generally endemic. The macropterous forms or the long winged adults of the insect are important in spreading the disease than the short winged forms. They feed on the diseased plant for at least 30 minutes to pick-up the virus. Higher infection is attained after prolonged inoculation feeding periods of up to 24 hours. The availability of the vector encourages the damage.
Mechanism of damage	Both nymphs and adults of brown plant hopper transmit grassy stunt virus. The insects can get the virus by feeding on diseased plants in a 6 hr-acquisition access period (minimum of 30 minutes). Longer feeding periods of up to 24 hours caused higher percentage of infected insects. After a latent period of 5-28 days (average of 10-11 days), the brown plant hoppers can transmit the virus in an inoculation access period of several minutes to 24 hr (minimum of 5-15 minutes). The infected insects can transmit the virus until they die.
Ideal management strategy	A single dominant gene governs resistance. A strain of wild rice, Oryza nivara Sharma & Shastry, was found to be resistant to the pathogen. The control of brown plant hopper, either with chemical, resistant varieties, or other control measures, result in the control of RGSV.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Hispa

Importance of the problem	The rice hispa is a defoliator seen during the vegetative stage of the rice plant. The pest is seen mainly during the planting and tillering period. The pest causes scrapping of upper surface and causes translucent white patches. The presence of two adults or two damaged leaves per hill is the time for adopting control measure.
Common signs and symptoms	• shiny blue-black adults scraping the upper surface of the leaf blade • scraping of upper surface of the leaf blade leaving the lower epidermis • damaged areas have white streaks that are parallel to the midrib • flat white larvae tunneling through leaf tissues as leafminers • tunneling through leaf tissue causing irregular translucent white patches that -are parallel to the leaf veins • Damaged leaves wither off • Damaged leaves turn whitish and membranous • Rice field appears burnt when severely infested
Problems with similar symptoms	The feeding damage is similar to the feeding marks caused by flea beetles.
Causal organism and their spread	Dicladispa armigera (Olivier) casuses the damage. The adult is blue-black and very shiny. Its wings have many spines. It is 5.5 mm long. Fresh egg is white. It is small and oval. It measures 1-1.5 mm long. With age, it turns yellow. A small dark substance secreted by the female covers each egg. The larva or grub is white to pale yellow. A younger grub measures 2.5 mm long and a mature larva is about 5.5 mm long. The pupa is brown and round. It is about 4.6 mm long. Close spacing causes greater leaf densities that favor the buildup of the rice hispa. The presence of grassy weeds in and near rice fields as alternate hosts harbor and encourage the pest to develop. Heavily fertilized field also encourages the damage. Heavy rains, especially in premonsoon or earliest monsoon periods, followed by abnormally low precipitation, minimum day-night temperature differential for a number of days, and high RH are favorable for the insect’s abundance.The rice hispa is common in rainfed and irrigated wetland environments and is more abundant during the rainy season.
Mechanism of damage	The larvae or grubs mine or tunnel inside the leaves as leaf miners. Then the larvae feed on the green tissues using their mandibulate mouthparts. During emergence, the adult beetle cuts its way out from the leaf. The adult insects are external feeders.
Ideal management strategy	A cultural control method that is recommended for the rice hispa is to avoid over fertilizing the field. Close plant spacing results in greater leaf densities that can tolerate higher hispa numbers. To prevent egg laying of the pests, the shoot tips can be cut. Clipping and burying shoots in the mud can reduce grub populations by 75-92%. Among the biological control agents, there are small wasps that attack the eggs and larvae. A reduviid bug eats upon the adults. There are three fungal pathogens that attack the adults. Spray with Quinalphos or Chlorpyriphos
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Leaf FolderAttack in Rice Field

Importance of the problem	The rice leaf folder is very common and can be found in all rice growth stages. The larvae of the pest feed the leaf while remaining inside it. The damage is important when it affects two fresh leaves per hill. And the damage at the reproductive stage can result in considerable yield loss. Therefore, management of leaf folder is very important in rice cultivation.
Common signs and symptoms	• Longitudinal and transparent whitish streaks on damaged leaves • Larvae fold a leaf blade together and glue it with silk strands. • Tubular folded leaves • Leaf tips sometimes fastened to the basal part of leaf • Heavily infested fields appear scorched with many folded leaves • Larvae feeds inside the folded leaf creating longitudinal white and transparent streaks on the blade • Folded leaves enclosing the feeding larvae • Disc-shaped ovoid eggs laid singly • Young larvae feeding on the base of the youngest unopened leaves • Fecal matter present
Problems with similar symptoms	The folded leaves are also symptoms similar to the ones caused by rice skippers and green semilooper. The whitish streaks are comparable to leaves damaged by rice whorl maggot and thrips.
Causal organism and their spread	There are three species of leaffolder and the adult moths can be distinguished by the markings on the wings. The adult is whitish yellow or golden yellow. It has three black bands on the forewings, either complete or incomplete. It has a wing span of 13 to 18 mm. The pupa is light brown or bright brown. With age, it turns reddish brown. It is 6 to 12 mm long. Neonate larvae are yellow. With age, they turn yellowish green with brown or black heads. They have distinct pinnaculae or one to two pairs of subdorsal spots on the mesonotum or metanotum. A third species lack spots on the notum. The apex of their pronotum is angulated, convex or always straight. They are from 8.5 to 25 mm long. The newly laid egg is jelly-like and transparent. It is oblong with an irregular upper surface. The mature egg is ovoid and whitish yellow. It is ventrally flattened.
Mechanism of damage	The larva forms a protective feeding chamber by folding a leaf blade together and glues it with silk strands and feed on leaf tissues. Longitudinal white and transparent streaks on leaf blades are created
Ideal management strategy	In cultural control, it is advised not to use too much fertilizer. It was observed in a field experiment that highly fertilized plots attract females. Surrounding grass habitats should be maintained because these serve as temporary reservoirs of natural enemies like crickets, which are egg predators of leaf folders. Herbicide spraying and burning of these non-rice habitats might not be useful. Among the biological control agents, there are small wasps and crickets that attack the eggs. The larval and pupal stages are parasitized by many species of wasps. Damselflies, ants, beetles, wasps, mermithids, granulosis virus, and nucleo-polyhedrosis virus prefer the larval stages. Spiders and mermithids attack the adults. Control of the rice leaf folders using chemicals during the early crop stages is not advisable. A general rule-of-thumb is “spraying insecticides for leaf folder control in the first 30 days after transplanting (or 40 days after sowing) is not needed.” The rice crop can compensate from the damage when water and fertilizer are well managed. Pyrethroids and other broad-spectrum insecticides can kill the larvae but can put the crop at risk because of the development of secondary pests, such as the brown planthopper. If infestations of the flag leaves are extremely high (>50%) during maximum tillering and maturity stage, insecticide sprays may be useful. Such applications may stop further defoliation and may avoid losses Spray with Bacillus thuringiensis @ 250 gram/ha Release of Trichoderma chilorius @ 5 cc/ha when moth activity is noticed. Spray with Acephate or Triazophos.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Ragged Stunt Virus

Importance of the problem	The disease is important during the tillering, reproductive, and maturity growth stages of the rice plant. The rice crop infected with the disease has partially exerted panicles and unfilled grains. Infected plants produce few or no grains at all depending on the extent of damage.
Common signs and symptoms	• Infected plants severely stunted during early growth stages of the crop • Leaves short and dark green with serrated edges • Leaf blades twisted at the apex or base, which result in the spiral shape of the leaves • Leaf edges uneven and the twisting give the leaves a ragged appearance • Ragged portions of the leaves are yellow to yellow-brown • Vein swellings develop on the leaf blades and sheaths • Swellings pale yellow or white to dark brown • Flag leaves twisted, malformed, and shortened at booting stage • Flowering is delayed • Incomplete panicle emergence • Nodal branches produced at upper nodes • Partially exerted panicles and unfilled grains • Presence of the vector Nilaparvata lugens (Stal) is an indication of RRSV disease.
Problems with similar symptoms	The ragged appearance and twisted leaf symptoms can be confused with the damage caused by rice whorl maggot and nematodes.
Causal organism and their spread	The brown plant hopper transmits the disease. The early instars nymphs of the insect are more efficient in transmitting the disease than older ones. Five-day-old nymphs are the most efficient transmitters. The virus is acquired within a feeding period of 24 hours. The virus is circulative and propagative in the insect vectors.
Mechanism of damage	The brown planthoppers can pick up the virus from infected plants in a 1 day acquisition access period. The latent period is 3-35 days (with an average of 8-6 days). The vectors transmit the disease in a 6 hour-inoculation access period (minimum of 1 hour). The vector retains the virus after each molt and remains infective for life.
Ideal management strategy	There are no specific control measures for the ragged virus disease except for the use of resistant varieties. Because some rice varieties are resistant to the brown plant hopper, to the virus, and to both. Cultivars resistant to the vector have low disease incidence. The application of insecticides to migratory plant hoppers is being used in temperate countries to reduce disease incidence.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Thrips

Importance of the problem	Rice thrips are seen as a serious pest during dry season. It infests the rice plant during the seedling stage or two weeks after early sowing. The damaged leaves have silvery streaks and will curl from the margin. The management is mostly dependent on the level of severity of the attack.
Common signs and symptoms	• Leaves damaged have silvery streaks or yellowish patches • Translucent epidermis becomes visible on damaged area • Leaves curled from the margin to the middle • Leaf tips wither off when severely infested • Unfilled grains at panicle stage • cream-colored eggs on leaf tissue with upper half of eggs exposed on leaf surface • yellow larvae and dark brown adults lacerate the plant tissues
Problems with similar symptoms	Rolled leaves are also symptoms of drought.
Causal organism and their spread	Rice thrips (Stenchaetothrips biformis (Bagnall) ) causes the problem. Rice thrips prefers rice and maize. It also feeds on Phalaris sp. and Imperata sp. Periods of dry weather favor the development of the rice thrips. No standing water in the rice fields encourages damage. The adult has a slender body. It is dark brown and 1-2 mm long. It exists in two forms, winged or wingless. The winged form has two pairs of elongated narrow wings that are fringed with long hairs. The adult thrips are day-flying. They migrate during the day and look for newly planted rice fields and other hosts. The pupa has long wing pads that reach two-thirds the length of the abdomen. It also has four pointed processes on the ninth abdominal tergite. The prepupa is brown. Four pointed processes are present on the hind margin of the ninth abdominal tergite. Neonate larvae are transparent and towards the second molting, they turn to pale yellow. The legs, head, and antennae of the second instar larvae are slightly darker than those of the first instar larvae. Neonate larvae feed on the soft tissues of unopened young leaves. Freshly laid egg is hyaline and turns pale yellow when about to mature. The egg is very tiny and measures 0.25 mm long. Eggs are laid in the slits of leaf blade tissue. The upper half of the egg is exposed.
Mechanism of damage	Both the larvae and the adults of rice thrips use their rasping mouthparts or their single mandible to lacerate the plant tissues. They utilize their maxillae and mouth cone to suck the plant sap.
Ideal management strategy	Flooding to submerge the infested field for two days as a cultural control practice is very effective against the rice thrips. Predatory thrips, coccinellid beetles, anthocorid bugs, and staphylinid beetles are biological control agents that feed on both the larvae and adults. Apply Dimethoate / Monocrotophos
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rice Whorl Maggot

Importance of the problem	The rice whorl maggot begins to infest the rice plant at transplanting stage. The insect does not prefer direct-seeded fields and seedbeds. The adult is active during the day and rests on rice leaves near the water. It locates rice fields by reflected sunlight from the water surface The rice plant can compensate for the damage caused by the rice whorl maggot. Usually, the symptoms disappear during the maximum tillering stage of the crop.
Common signs and symptoms	• White or transparent patches • Pinholes • Damaged leaves easily break from the wind • Somewhat distorted leaves • Clear or yellow spots on inner margins of emerging leaves • Stunting • Few tillers
Problems with similar symptoms	There are no other symptoms similar to those caused by the rice whorl maggot.
Causal organism and their spread	The adult fly is grey with transparent wings. It has a silvery white frons and cheeks. Its antennae are dark gray with 7-10 aristal hairs. The inner portion of the second antennal segment has silvery tinge. The fly has a grayish mesonotum with silvery white and brown tinges. Its scutellum is silvery white to grey. Its abdomen is silvery white to grey with blackish brown in the middle of the three basal segments. The adult fly has yellow legs except for the femora. The females are usually bigger than the males and are 1.5-3.0 mm long. The pupa is dark brown and subcylindrical. It measures 4.8 mm long. Its posterior end is tapering and has two terminal respiratory spines. The larva is legless. Neonate larva is transparent to light cream, whereas mature larva is yellowish. A mature larva is cylindrical with a pair of pointed spiracles found posteriorly. It is 4.4-6.4 mm long. The egg is whitish, elongate, and measures 0.65-0.85 mm long and 0.15-0.20 mm wide. It is banana-shaped with a hard shell covering.
Mechanism of damage	The larva uses its hardened mouth hooks to rasp the tissues of unopened leaves or the growing points of the developing leaves. The damage becomes visible when the leaves grow old. Mature larva prefers to feed on the developing leaves of the new developing tillers at the base of the rice plant.
Ideal management strategy	Small wasps parasitized the eggs and the maggots. Dolicopodid flies prey on the eggs and ephydrid flies and spiders feed on the adults. The rice plant can compensate for the damage caused by the rice whorl maggot. Usually, the symptoms disappear during the maximum tillering stage of the crop.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Rodents

Importance of the problem	Rodents are noted to consume and contaminate significant amounts of stored grain. Infested batches often have to be declared unfit for human consumption. There are around 50 diseases which can be transferred to man by rodents, including typhoid, paratyphoid, and scabies. In addition, rodents may be vectors of a large number of diseases affecting domestic animals. Therefore, management of rodents is very much important.
Common signs and symptoms	Feeding on stored produce. Rats eat an amount of food equivalent to 7% of their body weight daily, i.e. a rat with a body weight of 250 g will eat around 25 g daily, amounting to 6.5 kg of grain a year. Rodents contaminate the stored produce with urine, faeces, hair and pathogenic agents. Damage to material and equipment (e.g. tarpaulins, bags, pallets, sprayers) and to the store itself (cables, doors). Produce leaking out of damaged bags or storage containers Signs of rodent infestation Live animals: Rodents are mainly active at night. If animals are nonetheless seen during the daytime, this is a sign of an already advanced stage of infestation. Droppings: The shape, size and appearance of droppings can provide information as to the species of rodent and the degree of infestation. The droppings of Norway rats are around 20 mm in length and are found along their runs. The droppings of Black rats are around 15 mm long and are shaped like a banana. Mouse droppings are between 3 and 8 mm in length and irregular in shape. Droppings are soft and shiny when fresh, becoming crumbly and matt black or grey in colour after 2 - 3 days. Runs and tracks: Runs, such as those of Norway rats, are to be found along the foot of walls, fences or across rubble. They virtually never cross open areas of land, but always pass through overgrown territory, often being concealed by long grass. Runs inside buildings can be recognized by the fact that they are free of dust. The animal's fur coming into contact with the wall leaves dark, greasy stains. Even Black rats, which do not have any fixed runs, can leave similar greasy stains at points which they pass regularly, e.g. when climbing over roof beams. Footprints and tail marks: Rats and mice leave footprints and tail marks in the dust. If you suspect there might be rodent infestation, scatter some sort of powder (talcum powder, flour) on the door at several places in the store and later check for traces. The size of the back feet serves as an indication of the species of rodent: • Back feet larger than 30 mm: Black rat, Norway rat, Bandicoot rat. • Back feet smaller than 30 mm: House mouse, Multi-mammate rat, Pacific rat. Tell-tale damage: Rats leave relatively large fragments of grain they have nibbled at (gnaw marks). They generally only eat the embryo of maize. Sharp and small leftovers are typical for mice. Rodent attack can further be detected by damaged sacks where grain is spilled and scattered. Small heaps of grain beneath bag stacks are a clear sign. These should be checked for using a torch on regular controls. Burrows and nests: Depending on their habits, rodents either build nests inside the store in corners as well as in the roof area or in burrows outside the store. Rat holes have a diameter of between 6 and 8 cm, whereas mice holes are around 2 cm in diameter. These holes can be found particularly in overgrown areas or close to the foundations of a store. Urine: Urine traces are fluorescent in ultraviolet light. Where available, ultraviolet lamps can be used to look for traces of urine.
Problems with similar symptoms	The problems caused by rodents can be very well distinguished from other problems.
Causal organism and their spread	The most important rodent species are: Black rat or House rat (Rattus rattus) Norway rat or Common rat (Rattus norvegicus) House mouse (Mus musculus) Bandicoot rat (Bandicota bengalensis) The most essential factors for the occurrence of rodents are: sufficient supplies of food protected places in which to build burrows and nests hiding places access to produce
Mechanism of damage	Rodents are characterized by their teeth. They have a pair of incisor teeth in the upper and lower jaws. The incisors are curved inwards and have an extremely hard anterior coating. The softer inside layer is worn down much more rapidly than the hard, outer layer. This means that the teeth are continually kept sharp, enabling them to damage even materials such as masonry and electric cables. The incisors do not stop growing. This means that the animals are forced to gnaw steadily in order to wear them down.
Ideal management strategy	Keep the store absolutely clean! Remove any spilt grain immediately as it attracts rodents! Store bags in tidy stacks set up on pallets, ensuring that there is a space of I m all round the stack! Store any empty or old bags and fumigation sheets on pallets, and if possible in separate stores! Keep the store free of rubbish in order not to provide the animals with any places to hide or nest! Bum or bury it! Keep the area surrounding the store free of tall weeds so as not to give the animals any cover! They have an aversion to crossing open spaces. Keep the area in the vicinity of the store free of any stagnant water and ensure that rainwater is drained away, as it can be used as source of drinking water. The requirements of preventive rodent control must be taken into account whenever new stores are being built. Particular attention should be paid to doors, ventilation openings, brickwork and the junctions between the roof and the walls. Repair any damage to the store immediately! This applies especially to the doors.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Root Aphids

Importance of the problem	Rice root aphids are minor pests of rice. They are seldom widespread within a field. Rice root aphids are dominant in well-drained soils in upland and rainfed rice. They are not present in irrigated rice. A high number of aphids can cause yellowing and stunting once plant saps are removed.
Common signs and symptoms	• Leaf yellowing • Stunting if infestation is very severe • Globular and tan or brown nymphs and greenish, to brownish white, to yellow, to dark orange adults feeding on plants
Problems with similar symptoms	Except for the yellowing of the plant, stunting can be compared with the damage caused by root grubs.
Causal organism and their spread	Root aphid (Tetraneura nigriabdominalis) causes the damage. Both nymphs and adults of root aphid are causal organism. The adult is small and oval. Its color ranges from greenish, to brownish white, to yellow, and to dark orange. There are two adult forms: the winged and non-winged forms. The nymph is globular and tan or brown. Rice root aphids are favored by drought. Rice root aphids are dominant in well-drained soils in upland and rainfed rice. They are not present in irrigated rice. The adults are found on roots below ground level. They can also be located in cavities made by ants around the root system. The nymphs produce honeydew, which attracts ants. In return, ants transport the nymphs from plant to plant, protecting the growing aphids from predators and parasites.
Mechanism of damage	Both adults and nymphs of rice root aphid use their sucking mouthparts to remove plant fluids.
Ideal management strategy	There are natural enemies that can manage the population of rice root aphids. Both the nymphs and adults are parasitized by a small braconid wasp and a mermithid nematode and are preyed upon by lady beetles.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Root Grubs

Importance of the problem	Root grubs are minor insect pests of rice and seen usually in upland rice. Root grubs feed on rice during the seedling stage of the crop. During drought, damage caused by the insect pest is higher. Both the adults and larvae feed on the leaves and roots, respectively. Usually, the insects population will be naturally controlled without any management.
Common signs and symptoms	Orange-yellow leaves Wilting plants Stunted plants Root loss ovoid and creamy white eggs adults feeding on the leaves grubs or larvae feeding on the roots
Problems with similar symptoms	Other insect pests such as mealybugs and root aphids also cause plant stunting. The orange-yellow leaf symptom is similar in appearance to nutrient deficiency. The presence of the insect pest can confirm the symptom damage on the crop. The rice crop can be visually inspected for the damages such as damaged roots, abnormal height, and yellowish color of plants.
Causal organism and their spread	Leucopholis irrorata (Chevrolat) Root grubs generally prefer plants with fibrous root system. Root grubs are widespread in upland and rainfed rice environments. The adults are nocturnal and are attracted to light traps. Eggs are laid and developed in moist soil made by the burrowing females. In the soil, they usually remain close to where moisture is available. The adult beetle is black or dark brown in color. Its pronotum is not margined except for its lateral edges. The male has a longer antennal club than the female adult. While the female has a broader tibial spur with a rounded end, the male has a slender and pointed tibial spur. The pupa is dark brown. The grub is creamy white and has a pair of sclerotized mandibles. Three pairs of prominent legs are visible on the thoracic area and its body is curled in a C-shaped position. The eggs are pearly white and elongated or ovoid in shape. Aside from the rice plant, root grubs prefer plants with a fibrous root system such as maize, millet, sorghum, sugarcane and various grasses.
Mechanism of damage	The adults feed on the leaves while the grubs feed on the roots of rice plants by digging through the soil.
Ideal management strategy	The population of root grubs is generally controlled by natural biological control agents. Scoliid wasps parasitize the larvae. Carabid beetles, birds, toads, bats, and storks also eat the larvae and adults. The larvae are also infected by fungal pathogens. Drenching the root zone with Chlorpyriphos @ 5 ml/ liter.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Nematode Attack in Rice Cultivation

Importance of the problem	Root-knot nematode has recently started becoming an important pest of rice. The nematode cause characteristic hooked like galls on the root. The affected plant shows distorted and crinkled leaves and chlorosis. In upland rice, an estimated reduction of 2.6% in grain yield for every 1000 nematodes around seedlings is reported. Hence, controlling nematode is very important in rice cultivation.
Common signs and symptoms	• presence of the nematodes • stunting • chlorosis • early flowering and maturation • Characteristic hooked-like galls on roots • Newly emerged leaves appear distorted and crinkled along the margins • Heavily infected plants flower and mature early
Problems with similar symptoms	Other nematodes cause similar damage symptoms.
Causal organism and their spread	M. graminicola is a damaging parasite on upland, lowland and deepwater rice. It is well adapted to flooded conditions and can survive in waterlogged soil as eggs in eggmasses or as juveniles for long periods. Numbers of M. graminicola decline rapidly after 4 months but some egg masses can remain viable for at least 14 months in waterlogged soil. M. graminicola can also survive in soil flooded to a depth of 1 m for at least 5 months. It cannot invade rice in flooded conditions but quickly invades when infested soils are drained. It can survive in roots of infected plants. It prefers soil moisture of 32%. It develops best in moisture of 20% to 30% and soil dryness at rice tillering and panicle initiation. Its population increases with the growth of susceptible rice plants. The presence of relatively broad host range and many of the alternative vegetable crops that are grown during dry season are favorable for this nematode.
Mechanism of damage	Infective second stage juvenile of M. graminicola penetrates through the root tips and takes about a minimum of 41 hours. Females develop within the root and eggs are laid in the cortex. Galls are formed in 72 hours. The juveniles or immatures remain in the maternal gall or migrate intercellularly through the aerenchymatous tissues of the cortex to new feeding sites within the same root.
Ideal management strategy	Cultural control includes continuous flooding, raising the rice seedlings in flooded soils, and crop rotation. These practices will help prevent root invasion by the nematodes. Soil solarization, bare fallow period and planting cover crops such as sesame and cowpea has been reported to decrease nematodes. Rotation crop like marigold (Tagetes sp.) is also effective in lowering root knot nematode populations because of its nematicidal properties. There are some cultivars, which are resistant against the nematode. Several nematicidal compounds can be used as chemical control. They are volatile (fumigants) and nonvolatile nematicides applied as soil drenches and seedling root dips or seed soaks to reduce nematode populations. Seeds can be treated with EPN and carbofuran. The roots can be dipped in systemic chemicals such as oxamyl or fensulfothion, phorate, carbofuran, and DBCP. Telone (1,3- dichloropropene) can be injected into the soil before the crop is planted. Apply Carbofuran @ 18 kg/ha.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Effects of Salinity in Rice Cultivation

Importance of the problem	Salinity is defined as the presence of excessive amounts of soluble salts in the soil. It is usually measured as electrical conductivity (EC). Na, Ca, Mg, Cl, and SO4 are the major ions that cause slainity. When the concentration of these ions goes beyond certain range, growth of rice plant will be arrested. And the damage is more prominent during germination stage. Therefore, management of salinity is very much important in rice cultivation.
Common signs and symptoms	• Tips of affected leaves turn white • Chlorotic patches appear on some leaves • Symptoms first manifest themselves in the first leaf, followed by the second, and then in the growing leaf • Reduced plant height and tillering • Plant stunting and reduced tillering • Patchy field growth • Increased spikelet sterility • Reduced germination rate • Poor root growth • Salinity or sodicity may be accompanied by P deficiency, Zn deficiency, Fe deficiency, or B toxicity
Problems with similar symptoms	No other deficiency exhibits these symptoms but salinity.
Causal organism and their spread	Plant growth on saline soils is mainly affected by high levels of soluble salts (NaCl) causing ion toxicity, ionic imbalance, and impaired water balance. On sodic soils, plant growth is mainly affected by high pH and high HCO3- concentration. The major causes of salinity or sodicity are as follows: • Poor irrigation practice or insufficient irrigation water in seasons/years with low rainfall. • High evaporation. • Salinity is often associated with alkaline soils in inland areas where evaporation is greater than precipitation. • An increase in the level of saline groundwater. • Intrusion of saline seawater in coastal areas
Mechanism of damage	Salinity is defined as the presence of excessive amounts of soluble salts in the soil (usually measured as electrical conductivity, EC). Na, Ca, Mg, Cl, and SO4 are the major ions involved. Effects of salinity on rice growth are as follows • Osmotic effects (water stress) • Toxic ionic effects of excess Na and Cl uptake • Reduction in nutrient uptake (K, Ca) because of antagonistic effects The primary cause of salt injury in rice is excessive Na uptake (toxicity) rather than water stress, but water uptake (transpiration) is reduced under high salinity. Plants adapt to saline conditions and avoid dehydration by reducing the osmotic potential of plant cells. Growth rate, however, is reduced. Antagonistic effects on nutrient uptake may occur, causing deficiencies, particularly of K and Ca under conditions of excessive Na content. For example, Na is antagonistic to K uptake in sodic soils with moderate to high available K, resulting in high Na: K ratios in the rice plant and reduced K transport rates. Sodium-induced inhibition of Ca uptake and transport limits shoot growth. Increasing salinity inhibits nitrate reductase activity, decreases chlorophyll content and photosynthetic rate, and increases the respiration rate and N content in the plant. Plant K and Ca contents decrease but the concentrations of NO3-N, Na, S, and Cl in shoot tissue increase. Rice tolerates salinity during germination, is very sensitive during early growth (1-2-leaf stage), regains tolerance during tillering and elongation, but becomes sensitive again at flowering.
Ideal management strategy	• In rice-upland crop systems, change to double-rice cropping if sufficient water is available and climate allows. After a saline soil is leached, a cropping pattern that includes rice and other salt-tolerant crops (e.g., legumes such as clover or Sesbania) must be followed for several years. • Submerge the field for two to four weeks before planting rice. Do not use sodic irrigation water or alternate between sodic and nonsodic irrigation water sources. Leach the soil after planting under intermittent submergence to remove excess salts. Collect and store low saline rainwater for irrigation of dry-season crops (e.g., by establishing reservoirs). In coastal areas, prevent intrusion of salt water. • Apply Zn (5-10 kg Zn ha-1) to alleviate Zn deficiency. Apply sufficient N, P, and K. The application of K is critical because it improves the K: Na, K: Mg, and K: Ca ratios in the plant. Use ammonium sulfate as N source and apply N as topdressing at critical growth stages (basal N is used less efficiently on saline and sodic soils). In sodic soils, the replacement of Na by Ca (through the application of gypsum) may reduce P availability and result in an increased requirement for P fertilizer. • Organic amendments facilitate the reclamation of sodic soils by increasing the partial CO2 pressure and decreasing pH. Apply rice straw to recycle K. Apply farmyard manure. • Salinity can only be reduced by leaching with salt-free irrigation water. Because rice has a shallow root system, only the topsoil (0-20 cm) requires leaching. • Foliar application of K, particularly if a low-tolerance variety is grown on saline soil. Spray at the late tillering and panicle initiation stages.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Sheath Blight

Importance of the problem	Sheath blight is considered to be an important disease next to rice blast. The disease starts as greenish grey irregular lesions with dark lines on margins. And the disease incidence is noticed from the tillering stage onwards. Under favorable conditions, the disease increases as the plant grows older. Management of the disease should be taken up when 10 per cent or more tillers in the field is affected.
Common signs and symptoms	Initial lesions are small, ellipsoidal or ovoid, greenish-gray and water-soaked and usually develop near the water line in lowland fields Older lesions are elliptical or ovoid with a grayish white center and light brown to dark brown margin Lesions may reach the uppermost leaf under favorable conditions Lesions may coalesce forming bigger lesions with irregular outline and may cause the death of the whole leaf Severely infected plants produced poorly filled or empty grains, especially those on the lower portion of the panicles
Problems with similar symptoms	Lesions on the stem are sometimes confused with those caused by stem rot. Lesions on the stem resulting from stem borer infestation can be sometimes confused with sheath blight lesions.
Causal organism and their spread	Rhizoctonia solani Kunh (anamorph), The disease is soil borne. It usually starts at the base of the plant near the water level. Later, the symptoms are observed on the upper leaf sheath and on the leaf blade. The disease usually infects the plant at late tillering or early inter-node elongation growth stages. Disease may spread from one hill to another through leaf-to-leaf or leaf-to-sheath contacts. It is commonly assumed that the critical factors for disease development are relative humidity and temperature. Relative humidity ranging from 96 to 100% and temperature ranging from 28-32°C have been reported to favor the disease. High supply of nitrogen fertilizer, and growing of high-yielding, high-tillering, nitrogen-responsive improved varieties favor the development of the disease. High leaf wetness and high frequency of tissue contacts among plants also favor the disease. The pathogen can be spread through irrigation water and by movement of soil and infected crop residues during land preparation.
Mechanism of damage	The sclerotia germinate and initiate infection once they get in contact with the rice plant. The fungus penetrates through the cuticle or the stomatal slit. Infection pegs are formed from each lobe of the lobate appressorium of infection cushion. The mycelium grows from the outer surface of the sheath going through the sheath edge and finally through the inner surface. Primary lesions are formed while the mycelium grows rapidly on the surface of the plant tissue and inside its tissue. It proceeds upwards and laterally to initiate formation of the secondary lesions.
Ideal management strategy	Seeding rate or plant spacing should be optimized to avoid closer plant spacing or dense crop growth which favors the horizontal spread of the disease. Need-based or real-time application of nitrogen fertilizer is recommended in fields known to have a high amount of inoculum. Sanitation, specifically removing of weeds, can help control sheath blight considering that the pathogen also attacks weeds which are commonly found in rice fields. Removal of infected stubbles or crop residues from the field is also recommended to reduce the amount of inoculum for the succeeding cropping season. Spraying infected plants with fungicides, such as Carbendazim, and Propiconazole and antibiotics, such as validamycin is effective against the disease.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Sheath Rot

Importance of the problem	Sheath rot is an important disease of rice. It usually attacks the uppermost leaf sheath that encloses the panicles and causes rotting of the panicles. The disease is important during the heading stage of the crop. Infected panicles are discolored, sterile, shriveled, or with partially filled grain. Management of the disease should be taken up when 2-5 per cent or more tillers in the field is affected.
Common signs and symptoms	Infection occurs on the uppermost leaf sheath enclosing the young panicles at late booting stage Initial symptoms are oblong or somewhat irregular spots or lesions, 0.5-1.5 cm long, with dark reddish brown margins and gray center Lesions may also consist of diffuse reddish brown discoloration in the sheath Lesions enlarge and often coalesce and may cover the entire leaf sheath Severe infection causes entire or parts of young panicles to remain within the sheath Un emerged panicles rot and florets turn red-brown to dark brown Visible abundant whitish powdery growth inside the affected sheaths and young panicles Infected panicles are discolored, sterile, shriveled, or with partially filled grain
Problems with similar symptoms	Sheath rot lesions are sometimes confused with sheath blight lesions.
Causal organism and their spread	Sarocladium oryzae (Sawada) W. Gams & D. Hawksw High amount of nitrogen, high relative humidity, and dense crop growth favors sheath rot development. The fungus grows best at 20 to 28°C. The disease is host to Oryza sativa L. Its alternate host includes maize, pearl millet, sorghum, Echinochloa colona (L.) Link (jungle grass), Eleusine indica (L.) Gaertn. (goosegrass), Leptochloa chinensis (L.) Nees (red sprangletop), Oryza rufipogon (red rice), Zizania aquatica (annual wild rice), and Zizaniopsis miliaceae (giant cutgrass).
Mechanism of damage	No information on the mechanism of damage is available.
Ideal management strategy	Removal of infected stubbles after harvest and optimum plant spacing are among the cultural practices that can reduce the disease. Application of potash at tillering stage is also recommended. Foliar spray of calcium sulfate and zinc sulfate was found to control sheath rot. At booting stage, seed treatment and foliar spraying with carbendazim, or mancozeb was found to reduce sheath rot. Foliar spraying with benomyl was also found to be effective.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Soil too Soft

Importance of the problem	Rice need a good seed bed for proper germination and emergence. However, at times the soil become too soft. This mainly happens with clayey soils. In such cases, the seed will fail to get emerge properly. And it will create problems in crop establishment. Therefore, special care should be taken to prepare a good soil bed before sowing.
Common signs and symptoms	Plants fail to emerge, as seeds sink too deep and have problems of reaching the soil surface Pattern of damage across the field can be general, but often occurs in low spots of the field with standing water
Problems with similar symptoms	Various problems causing problems of crop establishment (e.g., cloddy soil, seed too deep, poor emergence in low spots in fields, heavy rainfall at seeding, soil crusting, poor seed quality, poor seed distribution, low seed rate, water stress, muddy water at seeding, clogged seeder and/or pests such as ants, birds and rats that remove seed at planting.)
Causal organism and their spread	The problem of soil being too soft occurs in wet direct seeded systems where insufficient time is given for the soil to settle between final wet land preparation (e.g., puddling) and sowing.
Mechanism of damage	In wet direct seeded fields, the seed should remain within 0.5 cm of the surface to adequately germinate and emerge. If the soil consistency is too soft, then the seed will sink into an anaerobic zone of the soil and the seed will have problems emerging resulting in poor stand establishment. Soil with high clay levels are often more prone to taking longer to settle.
Ideal management strategy	Ensure proper soil consistency at the time of sowing. A general rule of thumb is that the field is ready to be sown when a small “V” channel made in the soil with a stick holds it’s shape. If the small “V” collapses quickly, it is likely that the soil is still too soft for sowing.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Stem Borer Attack in Rice Field

Importance of the problem	Stem borer is a very important and common pest of rice. It causes dead heart or drying of the central tiller during the vegetative stage. And whiteheads,where the emerging panicles are whitish and unfilled or empty, in reproductive stage. The pest attack is more common in rice grown under flooded condition. Hence, controlling of stem borer is very much important.
Common signs and symptoms	Causes dead heart or drying of the central tiller during the vegetative stage Dead hearts or dead tillers can be easily pulled from the base during the vegetative stages Whiteheads during reproductive stage where the emerging panicles are whitish and unfilled or empty Tiny holes on the stems and tillers Frass or fecal matters inside the damaged stems Eggs seen in masses of 15- 80 covered with bluff-colored hairs on the upper leaf surface Neonate larvae suspend themselves from leaves by silken threads and blown to other plants to feed Mature larvae bore into the sheath and tiller of the plant
Problems with similar symptoms	Dead hearts and whiteheads symptoms may sometimes be confused with damages caused by rats, neck blast, and black bug diseases.
Causal organism and their spread	The larvae of yellow stem borer (Scirpophaga incertulas (Walker)) causes the damage. High nitrogenous field favours population buildup of the stem borers. Fields planted later favors more damage by the insect pest that early planted ones. Stubble that remains in the field can harbor stem borer larvae and or pupae. The female Yellow Stem Borer moth has a pair of black spots at the middle of each whitish, light brown to yellowish forewing. It has a wingspan of 24-36 mm. Its abdomen is wide with tufts of yellowish hairs all over. The male, gray or light brown in color, is smaller and has two rows of black spots at the tip of the forewings. It has a wingspan of about 20-30 mm. Its abdomen is slender toward its anal end and is covered with thin hairs dorsally. The Yellow Stem Borer pupa is pale green and measures about 12 mm long. It is enclosed in a white silk cocoon. Fresh cocoon is pale brown and turns dark brown with age. The first instar Yellow Stem Borer larva is about 1.5 mm long with yellowish green body. A full-grown larva has brown head and prothoracic shield and measures 20 mm. Second instar larvae enclose themselves in body leaf wrappings to make tubes and detach themselves from the leaf and falls onto the water surface. They attach themselves to the tiller and bore into the stem. The egg mass of Yellow Stem Borer is covered with brownish hairs from the anal tufts of the female. Individual eggs of are white, oval, and flattened.
Mechanism of damage	Stem borers feed on the crop during the vegetative and reproductive stages of the rice plant. Excessive boring through the sheath can destroy the crop. Its damage causes reduction in the number of reproductive tillers.
Ideal management strategy	Cultural control measures include proper timing of planting and synchronous planting. The crops should be harvested at ground level to remove the larvae in stubble. Likewise, stubble and volunteer rice should be removed and destroyed. Plowing and flooding the field can kill larvae and pupae in the stubbles. At seedbed and transplanting, egg masses should be handpicked and destroyed. The level of irrigation water can be raised periodically to submerge the eggs deposited on the lower parts of the plant. Before transplanting, the leaf-top can be cut to reduce carry-over of eggs from the seedbed to the field. Application of nitrogen fertilizer should be in split following the recommended rate and time of application. Biological control agents include braconid, eulophid, mymarid, scelionid, chalcid, pteromalid and trichogrammatid wasps that parasitize the eggs of yellow stem borer. Ants, lady beetles, staphylinid beetles, gryllid, green meadow grasshopper, and mirid bug also eat eggs. The larvae are parasitized by phorid and platystomatid flies, bethylid, braconid, elasmid, eulophid, eurytomid and ichneumonid wasps. They are attacked by carabid and lady bird beetles, chloropid fly, gerrid and pentatomid bugs, ants, and mites. Bacteria and fungi also infect the larvae. A mermithid nematode also attacks the larvae. Chalcid, elasmid and eulophid wasps parasitize the pupae. Ants and earwigs also eat the pupa. Bird, asilid fly, vespid wasp, dragonflies, damselflies, and spiders prey upon the adults. Cultivate tolerant varieties like IR-20 in endemic areas. In areas where stem borer occurs as a serious pest in all seasons, apply any one of the following insecticides first 15-20 days after transplantation and then at the boot leaf stage keeping minimum water level: Fenthion, quinalphos (spray or granules), fenitrothion, monocrotophos, carbofuran (granule), carbaryl. Use sex pheromone for the control of rice stem borer @ 8 traps /acre. And the critical time to adopt management practice is when you notice an adult moth or one egg mass in a meter square of space. Release of egg parasitoid Trichogramma japonicum @ 5cc /ha at weekly intervals from six week after transplantation. Application of carbofuran @ 18 kg/ha or Cartaphyrrochloride @ 10 kg/ha at 25 DAT and at booting stage.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Damage Caused by Storage Pests

Importance of the problem	Storage pest cause damage to rice after harvest. A number of factors at the time of harvest influence the build of storage pest in rice. An understanding of the common storage pest and their nature of feeding and damage help us in adopting appropriate management tactics.
Common signs and symptoms	Broken grains Powder of grains Holes in insect Black and brown small insects in grain
Problems with similar symptoms	Rodents cause damage to rice in storage stage.
Causal organism and their spread	Insects in stored rice can be classified into three groups according to their feeding habits namely internal feeders, external feeders and scavengers. Internal feeders are insects whose larvae feed entirely within the kernels of the grain. These includes rice weevil, angoumois grain moth and lesser grain borer. External feeders are insects that feed from the outside of the grain even though they may chew through the outer coat and devour the inside. These includes Cigarette or Tobacco Beetle (Lasioderma serricorne (Fabricius)), Flat Grain Beetle (Cryptolestes pusillus (Schonherr)) etc. Scavengers feed on the grain only after the seed coat has been broken either mechanically or by some other insect. eg. Saw-toothed Grain Beetle (Oryzaephilus surinamensis (Linnaeus)
Mechanism of damage	1. Internal Feeders These are insects whose larvae feed entirely within the kernels of the grain. Rice Weevil (Sitophilos oryzae (Linnaeus)): Adults and larvae feed on a wide variety of grains. Female deposits a single egg in the grain by boring a hole inside. The egg stays in the grain until it becomes an adult thus making the grain completely damaged. Angoumois Grain Moth (Sitatroga cerealella (Olivier)): Eggs are laid on or near grain. The white larvae bore into the kernels of the grain and feed on the inside. When mature, the larvae eat its way to the outer portion of the grain, leaving only a thin layer of the outer seed coat intact. Pupation takes place just under the seed coat. When the adult emerges from the grain, it pushes aside the thin layer of seed coat leaving a small trap door covering its exit point from the kernel. They infest only the surface layer of bulk-stored grain, adults are unable to penetrate deeply. Lesser Grain Borer (Rhyzopertha dominica (Fabricus)): The eggs are laid in the grain mass and larvae may enter the kernels and develop within or, they may feed externally in the flour-like dust that accumulates from the feeding of the adults and their fellow larvae. 2. External Feeders External feeders are insects that feed from the outside of the grain even though they may chew through the outer coat and devour the inside. Cigarette or Tobacco Beetle (Lasioderma serricorne (Fabricius)): Feeds on books, flax tow, cottonseed meal, rice, ginger, pepper, dried fish, crude drugs, seeds, pyrethrum powder, and dried plants. Flat Grain Beetle (Cryptolestes pusillus (Schonherr)): The female places her eggs loosely in the grain mass. The larvae and adults are able to penetrate the seed coat of the undamaged grain. 3. Scavengers Scavengers feed on the grain only after the seed coat has been broken either mechanically or by some other insect. Saw-toothed Grain Beetle (Oryzaephilus surinamensis (Linnaeus) Eggs are usually laid, either singly or in small masses, in a crevice in the food supply but in items like flour, they are laid freely.
Ideal management strategy	Before stacking the grains, go downs, store rooms or receptacle should be cleaned and made free from insects. Malathion at 15 ml of 50 % EC in 4.5 liters of water may be sprayed as a thin film on bags. The grains should be cleaned and dried well in the sun The bags should be stacked in such a way as to allow proper ventilation and sufficient moving space for periodic inspection. Heavily infected materials should be fumigated with Phosphine (1 tablet/tone) or hydrogen phospide or methyl bromide. The incoming new arrivals should not be stored along with old or infested stocks in the go down.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara. 3. KAU (2008) Crop Health Decision Support System (CD), Kerala Agricultural University, Vellanikkara.

Sulfur Deficiency Disorder in Rice Fields

Importance of the problem	Sulfur is a constituent of essential amino acids involved in chlorophyll production and protein synthesis. Its deficiency results in delayed plant development and maturity. Sulfur deficiency affects human nutrition by causing a reduction in cysteine and methionine content. However, Sulfur deficiency is not particularly common in irrigated rice and thus tends to be of little economic significance.
Common signs and symptoms	Young leaves chlorotic or light green colored with the tips becoming necrotic Lower leaves not showing necrosis Leaves pale yellow Yellowing or pale green whole plant Reduced plant height and stunted growth (but plants are not as dark-colored as in P or K deficiency) Reduced number of tillers, fewer and shorter panicles, reduced number of spikelets per panicle Delayed plant development and maturity by 1-2 weeks Yellowish seedlings in nursery beds with retarded growth High seedling mortality after transplanting S-deficient rice plants have less resistance to adverse conditions (e.g., cold)
Problems with similar symptoms	S deficiency is often not properly diagnosed, as foliar symptoms are sometimes mistaken for N deficiency.
Causal organism and their spread	S deficiency can be caused by: Low available S content in the soil. Depletion of soil S as a result of intensive cropping. Use of S-free fertilizers (e.g., urea substituted for ammonium sulfate, triple superphosphate substituted for single superphosphate, and muriate of potash substituted for sulfate of potash).
Mechanism of damage	Sulfur is a constituent of essential amino acids (cysteine, methionine, and cystine) involved in chlorophyll production and is thus required for protein synthesis, and plant function and structure. It is also a constituent of coenzymes required in protein synthesis. It is contained in the plant hormones thiamine and biotine, both of which are involved in carbohydrate metabolism. S is also involved in some oxidation-reduction reactions. It is less mobile in the plant than N so that deficiency tends to appear first on young leaves. S deficiency affects human nutrition by causing a reduction in cysteine and methionine content in rice.
Ideal management strategy	Apply S to the seedbed (rice nursery) by using S-containing fertilizers (ammonium sulfate, single super phosphate). Replenish S removed in crop parts by applying N and P fertilizers that contain S (e.g., ammonium sulfate [24% S], single super phosphate [12% S]). This can be done at irregular intervals. Calculate the cost-effectiveness of S supplied as S-coated urea or compound fertilizers containing S. Incorporate straw instead of completely removing or burning it. About 40-60% of the S contained in straw is lost during burning. Maintain sufficient percolation (~5mm per day), to avoid excessive soil reduction Carry out dry tillage after harvesting, to increase the rate of sulfide oxidation during the follow period.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Tungro Virus Disease in Rice Cultivation

Importance of the problem	Tungro is one of the most damaging and destructive virus diseases of rice. The disease affects all growth stages of the rice plant. The damage caused by the disease depends on the variety used, the stage of growth, the virus particles, and the environmental conditions. Plant infected with the virus at the early crop growth stage could have as high as 100% yield loss.
Common signs and symptoms	Discoloration begins from leaf tip and extends down to the blade or the lower leaf portion Infected leaves may also show mottled or striped appearance - stunting Reduced tillering Delayed flowering, which may delay maturity - panicles small and not completely exerted Most panicles sterile or partially filled grains and covered with dark brown blotches
Problems with similar symptoms	The yellowing of the plant and its stunted height is often confused with 1) physiological disorders such as nitrogen and zinc deficiencies and water stress; 2) pest infestation such as stem borer infestation, plant hopper infestation, and rat damage; and 3) other diseases such as grassy stunt virus disease and orange leaf disease.
Causal organism and their spread	Tungro virus disease is transmitted by leaf hoppers, wherein the most efficient vector is the green leafhopper, Nephotettix virescens (Distant). The disease complex is associated with rice tungro baciliform virus (RTBV) and rice tungro spherical virus (RTSV). RTBV cannot be transmitted by leafhoppers unless RTSV is present. Insects could acquire the virus from any part of the infected plant. After acquiring the virus, the vector can immediately transmit to the plants. Tungro incidence depends on the availability of the virus sources, population and composition of the vector, age and susceptibility of host plants, and synchronization of the three factors mentioned.
Mechanism of damage	The insect acquires the virus by feeding on the plant for a short time in an 8-hr acquisition access period (minimum of 30 minutes). It can transmit the virus immediately after feeding. Either or both viruses can be transmitted during a 1 hour inoculation access period (minimum of 7 minutes). The virus does not remain in the vector’s body. After feeding on a diseased plant, the insect can transmit the virus for about 5 days and the longest is about a week. The insect becomes re-infective after re-acquisition feeding.
Ideal management strategy	There are three limitations of effective tungro management: 1) the absence of symptoms at early growth stage of the disease development, 2) lack of resistant varieties to the tungro viruses, and 3) vector adaptation on GLH-resistant variety. Planting of resistant varieties against tungro virus disease is the most economical means of managing the disease. Among the cultural management practices, adjusting the date of planting is recommended. Likewise, observing a fallow period of at least a month to eliminate hosts and viruses and vectors of the disease and plowing and harrowing the field to destroy stubbles right after harvest in order to eradicate other tungro hosts are also advisable.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Udbatta Disease of Rice

Importance of the problem	Udbatta is a disease of rice affecting the whole panicle. The affected panicle will be completely covered with fungal mycelium and will look like an 'agarbatti'. There will be no grains on the affected panicle. However, the occurrence of the disease is very rare and therefore management practices should be adopted only in endemic areas.
Common signs and symptoms	The panicle emerges from the leaf sheath, as a straight, dirty coloured, hard, cylindrical spike considerably reduced in size, much resembling an agarbatti or udbatta Leaves of tender seedlings show lustrous greenish white appearance White mycelium and conidia form narrow stripes on the flag leaves along the veins before the panicle emerge No grains are formed on the affected ear
Problems with similar symptoms	The symptoms are very much characteristic of the disease
Causal organism and their spread	Ephelis oryzae The disease incidence is less severe on very early and late sown crops Plants like Cynadon dactylon and Isachne elegans serve as collateral host for the fungus.
Mechanism of damage	The fungus is externally seed born and systemic. The presence of lustrous grayish white films of fungal growth in young leaves of the infected seedlings suggest the entry of the pathogen during germination of the seeds. The diseased plants produce distorted ear heads later. Infection of the seeds is initiated at the time of emergence of the panicle. As no grains are obtained from affected heads, diseased seeds may not important for transmission of the diseases.
Ideal management strategy	Hot water treatment of the seeds at 50-54^oC for 10 minutes before sowing gives effective control of the disease. Solar treatment of the seed is effective in killing the pathogen carried in the seed. Avoid taking seeds from areas were the infection of the disease is noticed for the next season.
References	1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines 2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

Zinc Deficiency in Rice Cultivation

Importance of the problem

Zinc is an important micro-nutrient needed for various biochemical activities of rice plant. Deficiency of zinc can cause a reduction in yield. Its occurrence has increased with the introduction of modern varieties and crop intensification. Hence, checking of zinc in soil and adopting appropriate management strategy is very much important.

Common signs and symptoms

Symptoms appear between two to four weeks after transplanting
Dusty brown spots on upper leaves of stunted plants
Uneven plant growth and patches of poorly established hills in the field, but the crop may recover without intervention
Tillering decreases and can stop completely and time to crop maturity increases under severe Zn deficiency
Increase spike let sterility in rice
Chlorotic midribs, particularly near the leaf base of younger leaves
Leaves lose turgor and turn brown as brown blotches and streaks appear on lower leaves, enlarge, and coalesce
White line sometimes appears along the leaf midrib
Leaf blade size is reduced

Problems with similar symptoms

The symptoms of Zinc deficiency may resemble those of Fe deficiency, which also occurs on alkaline soils. On alkaline soils, Zn deficiency is often associated with S deficiency. They may also resemble Mn deficiency and Mg deficiency.
Leaf spots may resemble Fe toxicity in appearance but they latter occurs on high organic status soils with low pH.
Zn deficiency symptoms may resemble symptoms of grassy stunt and tungro virus diseases.

Causal organism and their spread

Zn deficiency can be caused by one or more of the following factors:

Small amount of available Zn in the soil.
Planted varieties are susceptible to Zn deficiency (i.e., Zn-inefficient cultivars).
High pH (close to 7 or alkaline under anaerobic conditions). Solubility of Zn decreases by two orders of magnitude for each unit increase in pH. Zn is precipitated as sparingly soluble Zn(OH)₂when pH increases in acid soil following flooding.
High HCO^3- concentration because of reducing conditions in calcareous soils with high organic matter content or because of large concentrations of HCO^3- in irrigation water.
Depressed Zn uptake because of an increase in Fe, Ca, Mg, Cu, Mn, and P after flooding.
Formation of Zn-phosphates following large applications of P fertilizer. High P content in irrigation water (only in areas with polluted water).
Formation of complexes between Zn and organic matter in soils with high pH and high organic matter content or because of large applications of organic manures and crop residues.
Precipitation of Zn as ZnS when pH decreases in alkaline soil following flooding.
Excessive liming.
Wide Mg:Ca ratio (i.e., >1) and adsorption of Zn by CaCO₃ and MgCO₃. Excess Mg in soils derived from ultrabasic rocks.

Mechanism of damage

Zinc is essential for several biochemical processes in the rice plant, such as:
• Cytochrome and nucleotide synthesis
• Auxin metabolism
• Chlorophyll production
• Enzyme activation
• Membrane integrity
Zn accumulates in roots and can be translocated from roots to developing plant parts. Because little re-translocation of Zn occurs within the leaf canopy, particularly in N-deficient plants, Zn deficiency symptoms are more common on young or middle-aged leaves.

Ideal management strategy

Dip seedlings or presoak seeds in a Zinc sulphate solution for 24 hours
Use fertilizers that generate acidity (e.g., replace some urea with ammonium sulfate). Apply organic manure.
Allow permanently inundated fields (e.g., where three crops per year are grown) to drain and dry out periodically. Monitor irrigation water quality.
If Zn deficiency symptoms are observed in the field, immediately apply 10-25 kg ha-1 ZnSO4.7 H2O. Uptake of ZnSO4 is more efficient when broadcast over the soil surface (compared with incorporated) particularly in direct-sown rice. To facilitate more homogeneous application, mix the Zn sulfate (25%) with sand (75%).
Apply 0.5-1.5 kg Zn ha-1 as a foliar spray (e.g., a 0.5% ZnSO4 solution at about 200 L water ha-1) for emergency treatment of Zn deficiency in growing plants. Start at tillering (25-30 DAT), two or three repeated applications at intervals of 10-14 d may be necessary. Zn chelates (e.g., Zn-EDTA) can be used for foliar application, but the cost is greater.

Zn fertilizers for rice:

Name	Formula	Content (% Zn)	Comments
Zinc sulfate	ZnSO₄ . H₂O ZnSO₄ . 7 H₂O	36 23	Soluble, quick-acting
Zinc carbonate	ZnCO₃	52-56	Quick-acting
Zinc chloride	ZnCl₂	48-50	Soluble, quick-acting
Zinc chelate	Na₂Zn-EDTA	14	Quick-acting
	Na₂Zn-HEDTA	9	Quick-acting
Zinc oxide	ZnO	60-80	Insoluble, slow

References

1. IRRI (2002) Rice Doctor, International Rice Research institute, Philippines
2. KAU (2002) Package of Practices Recommendations: Crops, Kerala Agricultural University, Vellanikkara.

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