桑天牛幼虫高毒力白僵菌菌株筛选

为利用白僵菌防治桑天牛,从野外感病死亡昆虫体上进行分离,同时利用黄粉虫对河北省土壤中的白僵菌进行诱集.诱集结果表明:白僵菌较多存在于自然的或人为活动较少的土壤中.利用获得的菌株对桑天牛幼虫进行生物测定,初步筛选出Bi05和Bs04 2个致病力较强的菌株,其接种10 d后的死亡率分别为96.47% 和92.93%,致死中时分别为4.53 d和4.83 d,而其他菌株的死亡率在28.59%和 82.12%之间,致死中时从5.84 d到16.4 d.利用不同孢子浓度的悬浮液对桑天牛幼虫进行接种,进一步测定了Bi05和Bs04菌株的致死中浓度分别为6.76×105 和1.39×106 conidia·mL-1.Bi05和Bs04菌株具有生物防治桑天牛的潜力.

Screening Test of Highly Virulent Strains of Entomopathogenic Fungi Beauveria bassiana against Apriona germari Larvae

To develop microbial control of Apriona germari, a destructive stem-boring pest, Beauveria bassiana were isolated from infected insects obtained in the field and by the bait method from soil samples in Hebei Province. The bait results showed that B. bassiana occurred more frequently in the natural and undestroyed soils.The virulence of all isolates was tested in bioassays by dipping larvae in 1×108 conidia·mL-1 suspensions. Two isolates Bi05 and Bs04 with the shortest LT50 value(4.53 d and 4.83 d) caused 96.47% and 92.93% mortality(due to B. bassiana)respectively 10 d post-inoculation while other isolates only caused mortalities from 28.59% to 82.12% with LT50 value ranged from 5.84 d to 16.4 d. The virulence of Bi05 and Bs04 was further tested by exposing A. germari larvae to conidial serial concentrations of 1×104～1×108 conidia·mL-1.LC50 value of Bi05 and Bs04 were 6.76×105 and 1.39×106 conidia·mL-1, respectively. The present results suggest that the isolate Bi05 and Bs04 has excellent potential for biological control of A. germari.