Sub-lethal effects of lufenuron exposure on spotted bollworm Earias vittella (Fab): key biological traits and detoxification enzymes activity

Spotted bollworm, Earias vittella, is one of the most serious and devastating insect pests of vegetables and cotton. Currently, insecticides are necessary for its control in nearly all crop systems. In this paper, we evaluate the sub-lethal effects of lufenuron on biological traits and activity of detoxification enzymes: cytochrome P450 monooxygenases, esterase, and glutathione S-transeferase (GST) in second instar larvae of E. vittella. Results showed that sub-lethal concentrations (LC₁₅ and LC₄₀ of lufenuron), prolonged larval period (at LC₄₀ = 13.86 ± 1.22 day, LC₁₅ = 13.14 ± 1.15 day, control = 12.28 ± 0.7), pupal duration (LC₄₀ = 11.1 ± day, LC₁₅ = 11.8 ± 0.28 day, control = 9.40 ± 0.52), and extended mean generation time (LC₄₀ = 27.3 ± 0.43 LC₁₅ = 29.0 ± 1.19 day, control = 26.0 ± 0.65). Sub-lethal exposure significantly prolonged the pre-adult stage, decreased pupal weight, and reduced adult longevity in the parent (F₀) and F₁ generation. Moreover, the fecundity and egg viability were significantly lowered in parental and F₁ generations at both sub-lethal concentrations compared to the control. While no significant effects were noted on reproductive parameters such as the intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R₀) of F₁ generation when compared to the control. Only mean generation time (T) in F₁ at LC₁₅ was significantly longer compared to the LC₄₀ and control (LC₄₀ = 3.79 ± 0.37, LC₁₅ = 32.28 ± 1.55 day, control = 29.79 ± 0.55). Comparatively, the activities of cytochrome P450 monooxygenases and esterase were higher than GST in treated populations. The increase in resistance development against insecticides may possibly because of elevated activity of detoxification enzymes. These results provide useful information for monitoring resistance in integrated pest management (IPM) programs for E. vittella.