Anthracnose Disease in Coffee

Importance of the problem

Anthracnose is a very important disease of coffee. It causes three different types of symptoms - twig dieback, brown blight of ripening cherries and leaf necrosis. This disease affects leaves, twigs as well as berries. This is generally a weak parasite but under certain conditions of the host and the environment becomes vigorously parasitic.

Common signs and symptoms

Brown blight of leaves
Round necrotic spots measuring up to 25 mm in diameter appear on leaves.
Two or more such spots may coalesce and the entire leaf or a portion of it may look blighted,
Necrotic spots are brown in colour hence the name brown blight.
Fructifications (acervuli) of the fungus are visible as black dots on the spots on upper or lower surface of leaf.
Twig die-back or summer die-back
Yellowing or blighting of any leaf on the green wood.
Twig wilts and defoliates, dries forward towards the apex and depicts a die-back appearance when quite dead.
Floral buds on the infected branches fail to open.
Affected plants put on new vegetative growth on the primaries and secondary near the main stem and this gives them a bushy appearance.
Profuse growth of suckers on the main stem takes place.
Affected plants in the exposed area bear the new leaves which are small, crinkled, chlorotic, thick and leathery.
Internodes are short and give a fan shaped appearance.
This disease occurs during dry weather from October to May and reaches peak levels after blossom showers.
Stalk rot of berries and leaves
Necrosis of nodes and internodes from the junction of brown and green wood towards the apex followed by berry drop and defoliation.
Berries and leaves drop down due to necrosis and decay of the stalk portion.
Generally, the rotting stalk remains on the branch while berries are shed.
Consequent to defoliation and berry drop is the death of tender twigs from the site of infection.
One or two nodes from the tip of the affected bunches may show total berry drop.
Brown sunken lesions on fully developed cherries which turn black and hard
Even if some berries remain, they show premature ripening towards the end of September-October and may remain as "lights" during crop harvest.

Problems with similar symptoms

Brown sunken lesions on fully developed cherries which turn black and hard can be confused with Cercospora leaf spot.

Causal organism and their spread

Anthracnose of coffee is caused by Colletotrichitm gloeosporioides. Low temperature, high relative humidity (95-100%), surface wetness of plants due to rain or mist, wounds on the stalk of berries and leaves and excess soil moisture during monsoon favors the spread of the disease.
Debility of twigs or branches due to defoliation, crop strain, inadequate overhead shade, prolonged drought and soil moisture stress favors the disease. The fungus invades the debilitated branches under the influence of low temperature. Mist or dew during night and early hours, increases sporulation of C. gloeosporioides on brown wood.

Mechanism of damage

The fungus on infection causes distraction to the plant tissue. This in turn causes considerable reduction in the photosynthetic area and yield loss 

Ideal management strategy

Twig die-back or summer die-back
Prune badly affected plants in February- March.
Protect the plants by spraying 0.5% Bordeaux mixture in February-March (preblossom), April-May (premonsoon) and September-October (postmonsoon). or pre and post monsoon spraying of Bavistin 50 W.P. (carbendazim) @ 0.03% at a.i. (120g/200 litres of water).
Maintain adequate overhead shade and leaf mulch around the plants to conserve soil moisture during dry weather,
Application of balanced nutrients to maintain vigour of the plants.
Stalk rot of berries and leaves
Premonsoon spraying of 0.5% Bordeaux mixture or 0.03% a.i. Bavistin 50 W.P. (carbendazim) @ 120g/200 litres of water in May-June, giving a good coverage of branches and stalk of berries.
Brown blight of leaves
Maintain good overhead shade to avoid sun scalding of leaves.
Spraying 0.5% Bordeaux mixture to protect the leaves from the rust fungus appears to give adequate protection against brown blight also.

References

1. CCRI (2003) Coffee Guide, Central Coffee Research Institute, Chikmagalur
2. Edward Winston, Jacques Op de Laak, Tony Marsh, Okkar Aung, Thaung Nyunt and Keith Chapman (2005) Arabica Coffee Manual for Myanmar, FAO Regional Office for Asia and the Pacific, Bangkok
3. Kerala Agricultural University. 2011. Package of Practices Recommendations: Crops. 14th edition. Kerala Agricultural University, Thrissur- 360 p.