Screening Of Virulent Strains Of Beauveria Bassiana To Brevicoryne Brassicae (L.) And The Study Of Its Characteristic

The eleven isolates of B. bassiana were cultured in spore-bearing yield, bourgeon rate and ultraviolet-radiation-resistant capacities. The strains were used to determine its virulence to Brevicoryne brassicae (L.) at different temperature and different concentration in laboratory. The death rate was to 93.87% at the temperature was 25℃and the concentration was 108. BD061-3 strain was higher than that of other strains in these respects.The optimum temperature for its growth and sprouting ranged from 25℃to 30℃. The optimum pH was 6.0 to 7.0. The optimum carbonaceous source was sugarcane and nitrogenous source was peptone.The biological compatibility of B.bassiana with five chemical insecticide was assayed. The results showed that Avermectin had strongly inhibitory effects on the germination rate, the high concentration made the conidia dead, the bourgeon rates of the medium and the low concentration were 11.29% and 11.06%. Imidacloprid, Chlorpyrifos, and Lambda-cyhalothrin had good biological compatibility, the bourgeon rates of the three concentration of the three chemical insecticide were 73.07%, 71.91%, 73.24%, 43.93%, 43.10%, 47.84%, 46.93%, 47.07% and 48.85%.When the mixtures of B. bassiana formulation with the three concentrations of Imidacloprid, Chlorpyrifos, or Lambda-cyhalothrin were stored at ambient temperature and at 4℃for months. When stored at ambient temperature, at the high concentration, none of the three chemicals was considered to be good enough for combining for a long time. But, Imidacloprid exhibited an encouraging long-term compatibility with B.bassiana at the low concentration. When stored at 4℃, B.bassiana formulation containing low and medium concentration of Imidacloprid retained the conidial viability up to 80% for 6 months.The high and medium concentration of Chlorpyrifos made the conidia dead on the 45th day and 150th day, the low concentration can be stored for 6 months and the conidial viability up to 77%. The high concentration of Lambda-cyhalothrin made the conidia dead after the 1st day, the medium and low concentration of Lambda-cyhalothrin made the conidia become low on the 4th day and 7th day.