Laboratory bioassay of soil insecticides against grubs of Brahmina coriacea (hope) (Scarabaeidae: Coleoptera) in Himachal Pradesh

Comparative bioefficacy of six insecticides viz. chlorantraniliprole, bifenthrin, clothianidin, thiamethoxam, imidacloprid and chlorpyriphos is reported in laboratory evaluation against grubs of Brahmina coriacea (Hope) through dip treatment. The LC₅₀ values of chlorantraniliprole for the three instars of grubs of B. coriacea were found to be 70.65, 213.30 and 226.1 ppm, while for bifenthrin, these were 100.20, 259.90 and 337.10 ppm respectively. Similarly, the LC₅₀ values of clothianidin for the three instars of grubs were 139.51, 266.12 and 348.30 ppm. Imidacloprid produced 50 per cent kill (LC₅₀) at a concentration of 156.12, 415.58 and 622.04 ppm in the three instars of grubs, and for thiamethoxam the respective LC₅₀ values were 205.89, 477.31 and 626.67 ppm. Chlorpyriphos was found to be least toxic among the tested chemicals. It produced 50 per cent kill of the three instars of grubs at concentrations of 222.60, 506.92 and 556.72 ppm, respectively.