Cross-resistance and biochemical mechanism in an insecticide-resistant population of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) and its parasitizing efficiency against invasive fall armyworm Spodoptera frugiperda (J.E. Smith)

Trichogramma chilonis is an egg parasitoid of lepidopteran pests and widely used in biological control and integrated pest management (IPM) programmes. In this study, the cross-resistance in multiple insecticide-tolerant strain of T. chilonis was evaluated against chlorantraniliprole 18.5% SC, spinetoram 11.7% SC and thiamethoxam 12.6% + lambda-cyhalothrin 9.5% ZC. Bioassay studies revealed the highest resistance level against chlorantraniliprole (8.83-fold resistance) over the susceptible population, followed by spinetoram (2.41-fold). Metabolic enzymes carboxylesterase and glutathione S-transferase showed major involvement in the resistant populations, with the highest activity obser­ved against chlorantraniliprole, followed by spinetoram. The resistant population at field recommended doses of chlorantraniliprole (400 ppm), parasitized 52.92% and 44.10% of Corcyra cephalonica and Spodoptera frugiperda eggs respectively, compared to 15.48% and 9.6% parasitism by the susceptible population. Integration and utilization of resistant strains of T. chilonis in IPM programmes can provide improved control of insect pests under insecticide-sprayed conditions and may reduce the insecticide load on crops