Interaction between Short-Term Heat Pretreatment and Avermectin on 2 nd Instar Larvae of Diamondback Moth, Plutella Xylostella (LINN)

Abstract

Based on the cooperative virulence index ( c.f.), the interaction effect between short-term heat pretreatment and avermectin on 2 nd instar larvae of diamondback moth (DBM), Plutella xylostella (Linnaeus), was assessed. The results suggested that the interaction results between short-term heat pretreatment and avermectin on the tested insects varied with temperature level as well as its duration and avermectin concentration. Interaction between heat pretreatment at 30°C and avermectin mainly resulted in addition. Meanwhile, pretreatment at 35°C for 2 or 4 h could antagonize the toxicity of avermectin at lower concentrations, which indicated a hormetic effect occurred. The results indicate that cooperative virulence index ( c.f.) may be adopted in hormetic effect assessment.