The interaction between short-term heat pretreatment and avermectin on 3rd instar larvae of diamondback moth,Plutella xylostella,was investigated.The results showed that the effect of short-term heat pretreatment at 35 ℃ on toxicity of avermectin varied with heat duration and avermectin concentration.Heat pretreatment at 35 ℃ for 2 hours,the interaction effect resulted in additive at all avermection concentrations,but in the trials for 4 h,antagonism was seen when avermectin was set at 1.13 mg/L or 2.25 mg/...