Influence of temperature on insecticidal toxicity and detoxifying enzymes to Spodoptera frugiperda

Increase in temperature due to global warming alters the relative abundance of insects and also affect insecticidal activity. In the present study we investigated the effect of temperature on the toxicity of five insecticides belonging to five different mode of actions groups according to Insecticide Resistance Action Committee (IRAC) viz., emamectin benzoate, spinetoram, chlorantraniliprole, novaluron and thiodicarb, against fall armyworm (FAW) Spodoptera frugiperda (JE Smith). We found that, as temperature increased from 20 to 41 ℃ the toxicity of chlorantraniliprole, emamectin benzoate, novaluron and thiodicarb increased to 8.26, 3.82, 1.97 and 1.94-fold respectively, showing positive temperature coefficient. Whereas, a 3.89-fold decrease in toxicity of spinetoram was observed, thus showing a negative temperature coefficient. The activity of detoxifying enzymes viz., glutathione-S-transferase (GST), carboxylesterase (CarE), and acetylcholinesterase (AChE) increased with the rise in the temperature whereas cytochrome P450 activity was inhibited. Significant correlation of median lethal concentration (LC₅₀) of these insecticides with AchE activity was observed for spinetoram (r = 0.968), novaluron (r = –0.967) and thiodicarb (r = –0.976). The study has implications for the management of S. frugiperda in diverse agroecological regions of India.