三株球孢白僵菌对草地贪夜蛾的毒力比较

为筛选有效防治草地贪夜蛾Spodoptera frugiperda的微生物制剂,采用室内生物测定法测定从北京市、浙江省和海南省土壤样品中分离获得的3株球孢白僵菌Beauveria bassiana菌株bbbj、bbzj和bbhn对草地贪夜蛾3龄幼虫的毒力,并比较这3株菌株的产孢情况和合成白僵菌素的能力。结果显示,分离自北京市的菌株bbbj对草地贪夜蛾3龄幼虫的毒力最强,LC50为3.37×105个孢子/mL;其次为浙江省的菌株bbzj,毒力略逊于菌株bbbj;海南省的菌株bbhn毒力最弱,其在试验最高浓度108个孢子/mL处理7 d后对草地贪夜蛾3龄幼虫的致死率低于50%。菌株bbbj的产孢量远高于另外2株菌株,并且其菌丝结构上着生大量芽生孢子簇,而且菌株bbbj菌体中的白僵菌素含量最高,培养5 d后,分别为菌株bbzj和bbhn的40.08倍和65.85倍。虽然补充白僵菌素可以提高菌株bbhn的毒力,但是草地贪夜蛾幼虫对白僵菌素敏感度不高。表明球孢白僵菌菌株bbbj对草地贪夜蛾幼虫有较高的毒杀活性,具有作为草地贪夜蛾生防菌株的潜力。

Comparison of virulence of three Beauveria bassiana strains against fall armyworm Spodoptera frugiperda

In order to screen microbial preparations for the effective control of fall armyworm Spodoptera frugiperda, the virulence of different Beauveria bassiana strains (bbbj, bbzj and bbhn) obtained respectively from soil samples from Beijing, Zhejiang and Hainan to the third-instar larvae was measured. The capacities of spore production and synthesis of beauvericin of three strains were compared. The results showed that the strain bbbj isolated from Beijing had the highest virulence with a LC₅₀ value of 3.37×10⁵ spores/mL, followed by the strain bbzj from Zhejiang, which was slightly less effective than bbbj. The mortality of the third-instar larvae of S. frugiperda treated with high concentration (10⁸ spores/mL) of bbhn strain from Hainan was lower than 50% in seven days. The spore production of bbbj was much higher than that of the other two strains. In addition, the content of beauvericin in strain bbbj was the highest, which was 40.08 times and 65.85 times of bbzj and bbhn, respectively, after five days of culture. However, although the supplement of beauvericin could improve the virulence of the strain bbhn, the sensitivity of S. frugiperda larvae to beauvericin was not high. The results indicated that the B. bassiana strain bbbj had high toxicity activity against the larvae of S. frugiperda and it had the potential to be used as a biological control strain.