Interaction Effect Between Short-term Heat Treatment And Pesticides On Larvae Of Diamondback Moth, Plutella Xylostella (Linn.)

Pesticides and short-term high temperature are 2 important factors that threaten the survival of diamondback moth,Plutella xylostella(Linn.).Based on the mortality as well as development rate and the toxicity of pesticides,the effect of short-term heat treatment on each life stage of P.xylostella was studied,the interaction between short-term heat treatment and pesticides on the 2^ndinstar larvae of P.xylostella was investigated and the value of pesticide interaction assessment method in hormesis study was discussed.The results were as follows:1 Effect of shor-term heat treatment on the survival and deveopment on each life stage of P.xylostellaHeat treatment at 30℃or 35℃affected a little on 1^stinstar larvae but no effect was found on other stages and these 2 temperatures could increase the development rate of each life stage except at 30℃for 4^thinstar lavae.Meanwhile,heat treatment at 40℃had sinificant effect on the survival of 1^stor 2^ndinstar larvae but not on egg,3^rdor 4^th instar larvae and could accelerate the development of egg and pupae.2 Interaction between short-term heat treatment and insecticides on the 2^nd instar larvae of P.xylostellaBased on the potention toxicity index(PTI),antagonism between the 2 factors occurred in some treatments.These include 2 h duration of 30℃prior to avermectin at 0.28 mg/L,2 h duration of 35℃prior to avermectin at 0.28 mg/L or 0.56 mg/L,4 h duration of 35℃prior to avermectin at 0.56 mg/L or 1.13 mg/L,2 h,4h or 8h duration of 30℃prior to fipronil at 0.39 mg/L or 0.78 mg/L,avermectin treatment at 0.56 mg/L prior to heat treatment at 35℃or 40℃for 2 h,fipronil treatment at 0.20 mg/L prior to heat treatment at 35℃for 2 h or 4h,fipronil treatment at 0.78 mg/L prior to heat treatment at 35℃for 2 h,fipronil treatment at 0.20 mg/L prior to heat treatment at 40℃for 2 h or 8h and fipronil treatment at 0.78 mg/L prior to heat treatment at 40℃for 2 h,4h or 8h.3 The reasonability of potentiation toxicity index in Hormesis assessmentThe results indicated that pesticide interaction assessment method could make Hormesis effect more obvious and may be adopted in Hormesis study.