Study on the Biological Characters of Isolates of Beauveria bassiana and their Virulence Against the Plutella xylostella

The biolgical characters of three isolates of Beauveria bassiana was tested,isolates were marked as DBM001,XWYE001 and PTM001.More over,the virulence against the diamondback moth,Plutella xylostella was evaluated.Among the tested isolates,no significant difference was found in spore yield,germination rate,as well as the mycelium growth rates on SDAY medium.But the virulence against diamondback moth was similar.A time-dose-mortality model was used for analyzing the mortality as affected by both time and dosage.The results showed that all tested isolates were virulent to the larvae of diamondback moth,accumulative mortality was 94.0%~48.0%,76.0%~28.0%,62.0%~28.0%.The value of LC50 for the these three isolate was 6.5×107conidia/mL;4.07×107conidia/mL;2.88×107conidia/mL,on the 3rd day after inoculation,the LT50 for the 3 isolates ranged from 3.0,3.5,4.1 days under the inoculation of 106 conidia/mL.