Abstract:

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.

Key words: Apriona germari, Beauveria bassiana, virulence, screening