author(s)
Tarikul Islam and Md. Jamil Hossain Biswas

abstract
The present research was conducted to study the toxic effect of entomopathogenic fungus Beauveria bassiana, three essential plant oils i.e. neem (Azadirachta indica A. Juss), mahogany (Swietenia mahagoni L.), and karanja oil (Millettia pinnata L.) and five biorational pesticides (spinosad, abamectin, emamectin benzoate, buprofezin and lufenuron) against adult Callosobruchus chinensis L. under laboratory conditions from January to October, 2016. Beauveria bassiana was found highly infectious and caused significant mortality of adult Callosobruchus chinensis populations after 24 hours of treatment application. Among the plant oils, karanja oil was found more toxic (LC₅₀ values were 0.139, 0.093 and 0.075% at 24, 48 and 72 hours after treatment application respectively) in laboratory bioassay compared to neem and mahogany oil. In case of biorationals, abamectin showed highest toxicity (LC₅₀ values were 0.081, 0.047 and 0.025% at 24, 48 and 72 hours after treatment application respectively) which was followed by emamectin benzoate and spinosad. However, Callosobruchus chinensis showed lowest susceptibility to buprofezin and lufenuron, two potential chitin synthesis inhibitors. The results of the present study clearly revealed that all the selected treatments could be successfully used as a grain protectant against Callosobruchus chinensis considering their LC₅₀ estimates.