Toxicity of microbial insecticide Bacillus thuringiensis Berliner vars Kurstaki and aizawasi to the larvae of Spodoptera litura Fabr. at different instars
2004
mangarengi, N., Morallo-Rejesus, B., Caoili, B.(Philippines Univ. Los Baños, COllege, Laguna (Philippines))
The life cycle of the cutworm, Spodoptera litura (Lepidoptera: Noctuidae), an imporatnt pest of many agricultural crops, was studied on castor leaves to ascertain the number and duration of larval instars prior to bioassay using Bacillus thuringiensis var Kurstaki and aizawai on the different instars. Two-day-old second, one-day-old third, and one-day-old fourth instar larvae of uniform sizes were used in the toxicity tests. Bt aizawa was more toxic than Bt Kurtaki to the second, third and fourth instar S. litura larvae both in the leaf and droplet feeding tests. The fourth instar larvae were more susceptible to Bt Kurstaki toxin than the second and third instar larvae which were comparable. regardless of instar, all the test larvae had comparable reactions to Bt aizawai, toxic both in the leaf dipping and droplet feeding tests. Both Bt varieties have good potential for use in the management of S. litura on different agricultural crops.
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