3-二辛硫基-1,1,1-三氟-2-丙烷(OTFP)对小菜蛾生长发育及农药敏感性的影响

Effect of 3-Octyl-1,1,1-trifluoro-2-propanone (OTFP) on Growth and Development and Insecticide Sensitivity of Diamondback Moth,Plutella xylostella

保幼激素是昆虫体内最重要的激素,保幼激素酯酶又是最重要的保幼激素代谢酶。为了探寻通过抑制保幼激素酯酶控制小菜蛾的可行性,测定保幼激素酯酶抑制剂3-二辛硫基-1,1,1-三氟-2-丙烷(OTFP)对小菜蛾(Plutella xylostella)3龄、4龄幼虫的毒力,研究OTFP对小菜蛾3龄幼虫蜕皮、4龄幼虫化蛹的影响,分析OTFP处理后小菜蛾3龄、4龄幼虫农药敏感性的变化。结果表明:OTFP对小菜蛾3龄幼虫、4龄幼虫的毒力都很低,但能显著延迟3龄幼虫蜕皮和4龄幼虫化蛹,而且影响随其质量浓度升高而加剧;OTFP处理后的3龄试虫对LC50时的丁醚脲、茚虫威、Bt、印楝素的敏感性显著下降,协同毒力指数都显著低于-20,达到拮抗水平,说明OTFP在所设质量浓度下,能够降低小菜蛾3龄幼虫对这几种农药的敏感性;但是对4龄幼虫,OTFP与以上4种农药的共毒系数都显著高于130,除个别处理外,OTFP与各农药在所研究质量浓度下协同毒力指数都大于0,并在几个处理中超过20,显示OTFP能够提高4龄幼虫对农药的敏感性。说明保幼激素酯酶抑制剂在小菜蛾控制中具有一定应用前景,但是若与农药配合使用,需要慎重选择使用时机、农药质量浓度等。

Juvenile hormone（JH）is the most important hormone in the insects and juvenile hormone esterase（JHE）plays the greatest role in its metabolism.To find out the possibility of controlling the diamondback moth（DBM）,Plutella xylostella,by means of JHE inhibition,the toxicities of 3-OctyL^-1,1,1-trifluoro-2-propanone（OTFP）,a specific JHE inhibitor,on both 3^rd and 4^thinstar larvae of DBM were tested,the effect of OTFP on the molting of 3rdinstar and pupation of the 4thinstar larvae was investigated and the insecticide sensitivity changes of both 3^rd and 4^thinstar larvae were measured.The direct toxicity of OTFP on either 3^rd or 4^th instar larvae of DBM was comparatively low,but it prolonged the molting of 3^rdinstar larvae and pupation of the 4^thinstar larvae in a dose-dependent way.The cooperative virulence indice（c.f.）between OTFP pretreatment and diafenthiuron,indoxacarb,Bt and azadirachtinin 3^rd instar DBM larvae were all lower than-20 suggesting that OTFP pretreatment antagonized the toxicities of the four insecticides to the 3^rd instar larvae at the set concentration.However,in 4^thinstar larvae,the co-toxicity indices（CTI）between OTFP pretreatment and the four above insecticides were all greater than 130 and the c.f.was positive in almost all treatments and even greater than 20 in several treatments,which indicated that OTFP pretreatment synergized the toxicities of the insecticides to the 4^thinstar larvae.Inferred from these,JHE inhibition helps for DBM control,but if combined with insecticide application,the administration time and the insecticide concentration should be taken into deep consideration.