Variation in the susceptibility of brinjal shoot and fruit borer Leucinodes orbonalis guenee to diamide insecticides and the role of detoxification enzymes

The susceptibility status of two field populations of brinjal shoot and fruit borer, Leucinodes orbonalis (Guenee) (Lepidoptera: Crambidae) collected from major vegetable growing regions of Kerala (Palakkad and Kollam) was determined during 2022–23 against diamide insecticides viz., flubendiamide 39.35% SC, chlorantraniliprole 18.5% SC, and cyantraniliprole 10.26% OD in comparison to the susceptible population. Palakkad and Kollam populations showed a shift in susceptibility to flubendiamide with an LC₅₀ value of 110.29 ppm and 23.987 ppm, respectively, as compared to that of the susceptible population with an LC₅₀ of 0.504 ppm. Similar trends were observed for chlorantraniliprole and cyantraniliprole in Palakkad population, with an LC₅₀ of 29.194 ppm and 3.399 ppm, respectively. Kollam population also showed a shift in susceptibility to chlorantraniliprole and cyantraniliprole with an LC₅₀ of 2.174 ppm and 0.23 ppm, respectively, as compared to that of the susceptible strain with an LC₅₀ of 0.119 ppm and 0.081 ppm, respectively. The wide range of variation among the field populations’ vulnerability to diamides might be attributed to the differential usage of these insecticides. The increased enzymatic activities of carboxylesterase, glutathione-S-transferase, and cytochrome P-450 monooxygenase in both populations emphasize the importance of detoxification enzymes in the metabolism of xenobiotics. These findings call for the judicious use of diamide insecticides to manage brinjal fruit and shoot borer.