施药后不同时间玉米田中常用农药残留对玉米螟赤眼蜂的影响

【目的】为明确玉米田中常用杀菌剂和杀虫剂对玉米螟赤眼蜂Trichogramma ostriniae的安全性。【方法】室内用田间推荐剂量在玉米叶片上施用4种杀菌剂(甲基硫菌灵、戊唑醇、叶枯唑和吡唑醚菌酯)以及4种杀虫剂(阿维菌素、氯虫苯甲酰胺、高效氯氰菊酯和吡虫啉)，施药后1, 3, 5和7 d调查玉米螟赤眼蜂成虫接触玉米叶片24 h时的死亡率、寄生能力(寄生的麦蛾Sitotroga cerealella卵量)及子代羽化率。【结果】施药后不同时间，不同杀菌剂和杀虫剂对玉米螟赤眼蜂成虫的死亡率、寄生能力和羽化率产生显著影响。4种杀菌剂中，叶枯唑和吡唑醚菌酯对玉米螟赤眼蜂寄生能力持续影响时间长，在施药7 d后，玉米螟赤眼蜂成虫接触含叶枯唑和吡唑醚菌酯残留的玉米叶片24 h时其寄生的麦蛾卵量分别为20.25和20.80粒；戊唑醇对玉米螟赤眼蜂的影响最大，施药7 d后玉米螟赤眼蜂成虫接触含戊唑醇残留的 玉米叶片24 h时子代羽化率为18.48%，施药3 d后接触时死亡率高达37.03%。4种杀虫剂中，阿维菌素和吡虫啉对玉米螟赤眼蜂寄生能力持续影响时间长并且毒性较大，在施药7 d后，玉米螟赤眼蜂成虫接触含阿维菌素和吡虫啉残留的玉米叶片24 h时的寄生的麦蛾卵量为3.43和9.19粒，施药后1-3 d时死亡率分别高达96.21%和74.00%；高效氯氰菊酯对玉米螟赤眼蜂子代羽化的持续伤害时间长，施药7 d后玉米螟赤眼蜂成虫接触含高效氯氰菊酯残留的玉米叶片24 h时的子代羽化率为27.92%。总体来说，4种杀虫剂对玉米螟赤眼蜂的影响较4种杀菌剂大。【结论】田间释放玉米螟赤眼蜂防治玉米螟Ostrinia nubilalis前7 d不建议喷施戊唑醇、叶枯唑和吡唑醚菌酯3种杀菌剂以及阿维菌素和吡虫啉两种杀虫剂，前5 d不建议喷施甲基硫菌灵和高效氯氰菊酯，氯虫苯甲酰胺使用时应该根据该药的田间推荐浓度合理喷施。

Effects of residues of pesticides commonly used in corn fields onTrichogramma ostriniae(Hymenoptera: Trichogrammatidae) at different time after application

【Aim】 This study aims to evaluate the safety of fungicides and insecticidescommonly used in corn fields to Trichogramma ostriniae. 【Methods】 Corn leaves wereapplied with four fungicides (thiophanate-methyl, tebuconazole, bismerthiazol, andpyraclostrobin) and four insecticides (avermectins, chlorantraniliprole,beta-cypermethrin, and imidacloprid) at the field recommended dosages in the laboratory.At 1, 3, 5 and 7 d after pesticide application, the mortality rates, parasitic abilities(numbers of Sitotroga cerealella eggs parasitized) and offspring emergence rates of T.ostriniae adults exposed to corn leaves containing pesticide residues for 24 h wereinvestigated. 【Results】 Different fungicides and insecticides at different time afterapplication had significant effects on the mortality rate, parasitic ability and emergencerate of T. ostrinia adults. Among the four fungicides, the effects of bismerthiazol andpyraclostrobin on the parasitic ability of T. ostrinia lasted for a long time. After 7 d ofapplication, the number of S. cerealella eggs parasitized by T. ostrinia adults exposed tocorn leaves containing bismerthiazol and pyraclostrobin residues for 24 h were 20.25 and20.80, respectively. Tebuconazole had the greatest effect on T. ostrinia. After T. ostriniaadults were exposed to corn leaves containing tebuconazole residue for 24 h, theiremergence rate was 18.48% at 7 d after pesticide application and their mortality was 37.03%at 3 d after pesticide application. Among the four insecticides, avermectins andimidacloprid had a more long-lasting effect on the parasitic ability of T. ostrinia andshowed greater toxicity. After T. ostrinia adults were exposed to corn leaves containingavermectins and imidacloprid residues for 24 h, the numbers of S. cerealella eggsparasitized were 3.43 and 9.19, respectively, at 7 d after pesticide application, and theirmortality rates were 96.21% and 74.00%, respectively, at 1-3 d after pesticide application.The emergence of T. ostrinia offspring was damaged for a longer time after application ofbeta-cypermethrin, and the offspring emergence rate was 27.92% at 7 d after application.In general, the four insecticides had a greater impact on T. ostriniae than the fourfungicides. 【Conclusion】 It is not recommended to use the three fungicides, tebuconazole,bismerthiazol and pyraclostrobin, and the two insecticides, avermectins and imidacloprid,in the field in 7 d before T. ostriniae are released to control Ostrinia nubilalis, and touse thiophanate-methyl and beta-cypermethrin in 5 d before T. ostriniae release.Chlorantraniliprole should be reasonably used depending on the recommended field dosages.