Effect of biopathogens (Bacillus thuringiensis Berliner and Beauveria bassiana Vuillemin) on different stages of egg plant spotted beetle, Henosepilachna vigintioctopunctata (Fab.) (Coleoptera: Coccinellidae).

摘要

The effect Bacillus thuringiensis var. kurstaki (B.t.) 0.25% suspension, and the white muscardine fungus, Beauveria bassiana (2 X 108 conidia/cm2) was studied on different stages of spotted beetle, Henosepilachna vigintioctopunctata [Epilachna vigintioctopunctata] infesting eggplant (Solanum melongena). B.t. used as a leaf dip caused a maximum mortality of 68.9% in the first instar larvae and a minimum of 13% in the prepupal stage of the pest. The adults were less susceptible to B.t. The per cent egg hatchability was, respectively, 12.2, 11.7, 17.9, 12.9 and 18.7 when freshly laid, 1-, 2-, 3- and 4-day old eggs were treated with 0.25% B.t. Direct spraying of B. bassiana killed 58.1% first instar larvae and 35.2% pre-pupal stage larvae. The adultswere not susceptible to B. bassiana, the maximum mortality being 10.3% in the case of newly emerged adults. B. bassiana caused 54.6% hatchability of one-day old eggs of the spotted beetle.