Antifeedant effect of emulsifiable concentrate formulation of Ageratum conyzoides (L.) (Asteraceae) extracts against Plutella xylostella (L.) (Lepidoptera: Plutellidae)

The diamondback moth (DBM), Plutella xylostella, is a highly destructive cosmopolitan pest of cruciferous crops, causing severe economic losses worldwide. The research work aimed to evaluate the antifeedant activity of methanolic extracts of Ageratum conyzoides leaves and its emulsifiable concentrate (EC) formulations against diamondback moth larvae in both no-choice and two-choice bioassays under standard laboratory conditions. In both no-choice and two-choice bioassays, a concentration-dependent reduction in feeding was observed when cauliflower leaf discs were treated with methanolic extract and its EC formulation was offered to the fourth-instar DBM larvae. The antifeedant index (AFI) values were positively correlated with different concentrations of crude extracts (R² = 0.992) and EC formulations (R² = 0.941). Moreover, the EC formulation of foliar extracts showed a substantial deterrent effect on the feeding behaviour of diamondback larvae compared to crude extracts. Our results provide environment-friendly substitutes to synthetic chemical-based insecticides for the management of diamondback moth.