常用化学农药对球孢白僵菌HFW-05菌株的影响及其混用对小菜蛾的联合毒力

Effects of Chemical Pesticides on Entomopathogenic Fungus Beauveria bassiana HFW-05 Strain and the Joint Toxicity of Their Mixtures against the Diamondback Moth,Plutella xylostella(L.)(Lepidoptera:Plutellidae)

球孢白僵菌HFW-05对粉虱有很高的杀虫活性,为扩大该菌株的杀虫范围及明确其与常用化学农药的混用效果,测定了HFW-05菌株对小菜蛾的杀虫活性及化学药剂对HFW-05菌株孢子生长发育的影响。结果表明,HFW-05菌株对小菜蛾幼虫表现出很高的杀虫活性,5×107孢子/mL浓度下,HFW-05菌株对小菜蛾2,3龄幼虫的6 d校正死亡率分别为86.7%和76.7%,各试验浓度下对2龄小菜蛾幼虫的毒力显著高于3龄幼虫。随浓度降低化学药剂对孢子萌发的抑制作用均明显减弱,药剂对孢子的影响与菌药混用时对昆虫的毒力影响没有明显的相关性。常规用量下,抑太保、三氟氯氰菊酯和辛硫磷强烈抑制孢子萌发,孢子萌发率为0,0和7.9%,药剂5倍稀释液与1×106孢子/mL孢悬液混用,辛硫磷、灭多威、灭幼脲Ⅲ号对小菜蛾表现为拮抗作用,校正死亡率分别为23.4%,16.2%和20.5%,其余药剂均表现为毒力相加作用,抑太保、氟虫脲的增效作用显著,对小菜蛾的校正死亡率分别为93.3%和98.0%。可见菌药合理混用对改善小菜蛾的生物防治有一定的指导意义。

Beauveria bassiana HFW-05 strain is highly virulent against Bamisia tabaci.To broaden its insecticidal range and determine the joint toxicity of the mixtures of conidia spores and chemical pesticides,the bioassay of HFW-05 strain to 2nd and 3rd instar larvae of diamondback moth,Plutella xylostella（L.） and the conidia germination and mycelia growth of HFW-05 were carried out.The results showed that HFW-05 strain was highly toxic to larvae of diamondback moth.The corrected motality of conidia spores of the concentration 5 107/mL to 2nd and 3rd instar larvae 6 d after infection were 86.7% and 76.7% separately,and the toxicity to the 2nd instar larvae was markerdly higher than to 3rd instar larvae at all tested concentration.The inhibitory action of chemical agents on spores was significantly reduced with decreasing concentration.There was no significant correlation between the impact of chemicals on spores and the toxicity of fungus mixed drug to P.xylostella.At conventional dosage,chlorfluazuron,cyhalothrin and phoxim strongly inhibited spores growth with 0,0 and 7.9% germination respectively.The virulence of 5-fold dilution of phoxim,methomyl and diflubenzuron Ⅲ mixed 1×106 /mL spores to the P.xylostella exhibited antergic with corrected mortality 23.4%,16.2% and 20.5% respectively.But the other agents showed additive effect for the toxicity to P.xylostella.Chlorfluazuron and fipronil showed significant synergistic activity with corrected mortality 93.3% and 98.0% separately.This result may be used to improve biocontrol of the pest.