Bacillus thuringiensis (Bt)
The bacterium Bacillus thuringiensis (Bt) is a used against control of insect pests. It is mainly effective against caterpillars. After eating leaves that are covered with the product, the caterpillars slow down and die after few days.
Bt is available commercially under the trade names Dipel, Halt, Delfin etc., and is recommended as a foliar spray. Bt can withstand higher temperatures and can be used like any other normal insecticide.
Two to three sprays of Bt at a dose 1.0-1.5 gram/liter of water depending on the stage of the larva at 10 days interval should be undertaken for the management of caterpillar pests. For best results, sprays should be undertaken when the larvae are in 2nd or 3rd instar.
For management of H. armigera on red gram, three sprays of Bt. (2.5gm/litre of water) need to be undertaken from initiation of flowering at 10 days interval.
Take care to store the bio control agents in cool places. Never mix it with chemical fertilizers or pesticides. Always use before the date of expiry.