Stage-specific Toxicity and Efficacy of Different Insecticides in the Management of White Grub (Brahmina coriacea)

Abstract

Brahmina coriacea (Hope) is a prominent white grub species and a serious soil-dwelling pest, causing considerable damage to various agricultural and horticultural crops in the northwestern Himalayan region of India. The present study assessed the toxicity of selected insecticides against third-instar grubs, adults, and eggs of B. coriacea under laboratory conditions. Among the tested insecticides, chlorantraniliprole was the most effective across all life stages, recording the lowest LD50 values in grubs (1.41 μg per grub) and adults (0.23 μg per beetle), and the highest egg mortality (53.14%). Bifenthrin showed comparable toxicity to chlorantraniliprole in grubs, while carbofuran and chlorpyriphos exhibited moderate effectiveness; fipronil was consistently the least toxic. Adults were more susceptible than grubs, as indicated by lower LD50 values. Egg mortality increased significantly with exposure period, i.e. 18.43% at 3 days to 49.44% at 14 days after treatment, demonstrating a clear time-dependent effect. Overall, chlorantraniliprole emerged as the most potent insecticide against B. coriacea. The findings highlight the importance of considering life-stage differences in insecticide efficacy and provide a scientific basis for optimising pest management strategies targeting B. coriacea.