Adverse effect of Bacillus thuringiensis Berliner on silkworm, Bombyx mori L. and other beneficial nontarget organisms

Adverse effect of Bacillus thuringiensis var. kurstaki (176000 IU/mg) against different larval instars of silk worm, Bombyx mori L. was studied using different concentrations under laboratory condition at 20.2°–28°C and 78.1–91.0% r.h. The biocide B.t.k. was highly toxic to B. mori and 0.1% concentration of B.t.k. provided 90.0% and 96.67% mortality in 3^rd and 4^th instar larvae of B. mori respectively. Even a low concentration of B.t.k. −0.01% inflicted 56.67% mortality of the 4^th instar larvae. The LC₅₀ values of 3^rd, 4^th, and 5^th instar larvae of B. mori were 0.022%, 0.013% and 0.089% B.t.k. respectively. B.t.k. formulation used in the experiment was almost safe to 4 species of nontarget organisms comprising of tadpoles, Buffo melanotictus; earthworm, Pheretima posthumo; fresh water fish, Cyprinus carpio and millipedes, Julus sp.