绿僵菌素对爪哇棒孢霉SP053菌株的影响及其混用对小菜蛾的联合毒力

Effects of destruxins on entomopathogenic fungus Isaria javanicus and the joint toxicity of their mixtures against the diamondback moth,Plutella xylostella(L.)(Lepidoptera:Plutellidae)

为了寻找更有效的利用虫生真菌爪哇棒孢霉Isaria javanicus防治小菜蛾Plutella xylostella的新方法,测定了绿僵菌素(destruxin)对SP053菌株生长发育与产孢量与萌发率的影响,利用协同毒力指数法和毒力回归分析法评价了两者混用对小菜蛾2龄幼虫的联合毒力。结果表明:绿僵菌素对SP053菌株菌丝生长、孢子萌发率和孢子产量均无显著影响(P>0.05)。而一定浓度的绿僵菌素与SP053菌株分生孢子混用具有增效作用,S50-CD100(指爪哇棒孢霉SP053菌株的分生孢子浓度为50×105个/mL和绿僵菌素粗毒素的浓度为100mg/L的组合;依此类推)、S25-CD100、S25-CD50及S12.5-CD100等混配组合都有显著的增效效果,尤其以S25-CD100组合增效效果最好,其48h和72h的协同毒力指数(c.f.)分别达到52.31和31.07。毒力回归分析结果也显示,添加绿僵菌素粗毒素25～100mg/L的混剂的LC50值明显降低,比如添加100mg/L绿僵菌素粗毒素的混剂(SP053-CD100),其48和72h的LC50分别为17.45和10.55(×105个孢子/mL),而SP053菌株分生孢子单剂的LC50相应值为>50和35.85(×105个孢子/mL)。本研究证明绿僵菌素与爪哇棒孢霉SP053菌株混用有增效作用,对改进小菜蛾的生物防治方法有一定指导意义。

In order to find a faster and more effective method to use entomogenous fungus Isaria javanicus to control the diamondback moth,Plutella xylostella （L.）,bioassays were carried out to clarify if destruxins can influence mycelia growth production and germination of conidia spores of the strain SP053,and to evaluate their joint toxicity against the 2nd instar larvae of P. xylostella. The results indicated that destruxins had no significant effect （P0.05） on strain growth and conidia production and germination. However,there was certain synergism between destruxins and conidia spores of the strain SP053. The mixtures of S50-CD100 （meaning the mixture of conidia spores of the concentration 50×105/mL and crude destruxin of the concentration 100 mg/L other mixtures indicated in the same way）,S25-CD100,S25-CD50 and S12.5-CD100 showed distinct synergism. The S25-CD100 combination showed the highest effectiveness with the cooperative virulence index （c.f.） reaching 52.31 and 31.07 at 48 and 72 h after treatment,respectively. This synergism was verified by virulence bioassay as well. The mixtures contained crude destruxin （CD） from 25 to 100 mg/L had lower LC50 values,for example,the LC50 values of the mixture SP053-CD100 （containing CD 100 mg/L） at 48 and 72 h were 17.45×105 and 10.55 ×105 spores/mL,respectively meanwhile,those of the control （without destruxins） were 50×105 and 35.85 ×105 spores/mL,respectively. It is so concluded that the mixing of destruxins and the I. javanicus strain SP053 has synergism against P. xylostella. This result may be used to improve biocontrol of the pest.