Toxicity of Bacillus thuringiensis varieties kurstaki and aizawai against some lepidopterous pests.
The toxicity of B. thuringiensis vars. kurstaki and aizawai was evaluated against some lepidopterous larvae by leaf/fruit dip method. The substrates (leaves/fruits) were dipped in the respective dilutions (2 g/l of water) of the commercial formulations for 5 sec and dried at room temperature. Larvae of the test insect were released on the treated food. Mortality of the test insect was recorded 1, 3, 5 and 7 days after their release. The larvae of Antigastra catalaunalis were observed to be the most susceptible to both the varieties of B. thuringiensis showing 100% mortality one day after release. Per cent mortality of larvae of Euproctis lunata, Cnaphalocrocis medinalis, caseworm (unidentified), Earias vittella, Plutella xylostella, Spodoptera litura and Helicoverpa armigera, was recorded after seven days of release, which was found to be 60, 75, 80, 98.9, 100 and 75.1%, respectively, when these were fed with B. t. var. kurstaki treated food. The corresponding figures with respect to B. t. var. aizawai were 48, 67.9, 72.3, 71.2, 85.4, 93.7 and 72.4%, respectively.