author(s)
Swapnalisha Mohapatra and Inee Gogoi

abstract
A laboratory bioassay was carried out to determine the LC₅₀ and relative toxicity of three botanicals (leaf extracts) along with a check imidacloprid 17.8 SL and control to manage the effect of aphid, Aphis craccivora Koch in cowpea. Among the plant extracts tested Ocimum sanctum showed the lowest LC₅₀ value (0.316) followed by Ageratum conyzoides (2.381) and Lantana camara (3.200) after 72 hours exposure period. Considering the relative toxicity of imidacloprid as unit value the comparison of relative toxicity revealed that O. sanctum, A. conyzoides and L. camara were 0.098, 0.013 and 0.010 times less toxic than imidacloprid after 72 hours exposure respectively. The order of relative toxicity was found in the following manner: O. sanctum>A. conyzoides>L. camara.