溴虫腈对几种桑园害虫和家蚕的室内毒力测定及在田间防治的选择性毒力调查

研究杀虫、杀螨剂溴虫腈在桑树害虫与非靶标昆虫家蚕之间以及桑树害虫之间的差异性毒力,为溴虫腈在桑园安全、合理使用提供依据。采用浸叶法测定24%溴虫腈悬浮剂对野桑蚕、家蚕、桑螟、桑尺蠖的室内毒力选择性比值较高,其LC50值倍数比例为362∶126∶1.6∶1,各种试虫对该药剂的敏感程度从大到小依次是桑尺蠖>桑螟>家蚕>野桑蚕,该药剂对家蚕的毒性很小。分别采用80、160、320 mg/L 3种质量浓度溴虫腈悬浮剂稀释液喷施桑树后间隔1、3、6、9 d采摘桑叶饲养家蚕3龄幼虫至上蔟,除用320、160 mg/L溴虫腈悬浮剂稀释液处理区间隔1 d的桑叶养蚕后,家蚕的各项生理指标与清水对照区差异极显著(P<0.01)外,其它处理区无显著差异(P>0.05),并无迟发性毒性效应。田间防治试验表明,24%溴虫腈悬浮剂对桑树害虫的毒力具有选择性,试验期桑园内的几种害虫对该药剂的敏感程度从大到小依次是桑尺蠖>桑螟>桑毛虫>桑剌蛾,320、160、80 mg/L 3种质量浓度溴虫腈悬浮剂稀释液喷施后7 d对桑尺蠖的平均防效极显著优于对照农药267 mg/L辛硫磷稀释液的防效,而对桑螟的平均防效低于对照农药200 mg/L灭多威稀释液的防效(94.2%)。研究结果显示溴虫腈用于桑园害虫防治具有一定的选择性毒力,对非靶标生物家蚕的毒性较低,该药剂适合用于对桑尺蠖等桑园害虫的防治。

Determination on Indoor Toxicity of Chlorfenapyr to Major Mulberry Pests and Silkworm and Investigation on Its Selective Toxicity in Field Application

Understanding the toxicity differences of chlorfenapyr,an insecticide and acaricide,between mulberry pests and silkworm(Bombyx mori),a non-target insect,and between different mulberry pests would provide guidance for its safe and reasonable application in mulberry filed.In this study,we used four insect species,i.e.Bombyx mandarina,Bombyx mori,Diaphania pyloalis,and Phthonamdria atrineata,as materials to measure the toxicity differences of 24% chlorfenapyr suspend emulsion by leaf soaking method.The results showed that their LC50 values were in a ratio of 362:126:1.6:1,and their sensitivity to this agent was in the order of Phthonamdria atrineata>Diaphania pyloalis>Bombyx mori>Bombyx mandarina,indicating that the agent had a low toxicity to silkworm.With three different concentrations(80,160,and 320 mg/L) of chlorfenapyr suspend emulsion to spray onto mulberry trees,mulberry leaves were harvested to feed the silkworm larvae from the 3rd instar till cocoon spinning after 1,3,6,and 9 d.The results showed that,except the treatments with 320 and 160 mg/L of chlorfenapyr suspend emulsion of which various physiological indexes of silkworm larvae feeding on mulberry leaves harvested 1 d after the treatment had extremely significant difference(P<0.01) with those of the clean water control group,there were no significant differences(P>0.05) between all other treatments and the check group and no delayed toxic effect either.Field prevention experimental results showed that 24% chlorfenapyr suspend emulsion had selective toxicities to mulberry pests.Within the survey period,the sensitivity of major mulberry pests to this agent was in the order of Phthonamdria atrineata> Diaphania pyloalis>Euproctis similis>Thosea postornata.The average control effect of chlorfenapyr suspend emulsion to Phthonamdria atrineata at 7 d after application with 320,160 and 80 mg/L dilutions was extremely significantly superior to that of the control pesticide 267 mg/L phoxim,but that to Diaphania pyloalis was lower than that of the control pesticide 200 mg/L methomyl(94.2%).The results indicated that chlorfenapyr has certain selective toxicity for controlling mulberry pests,with very low toxicity to silkworm,the non-target organism,and thus being suitable for controlling Phthonamdria atrineata and other pests in mulberry field.