Study On Wettable Powder Of Beauveria Bassiana And Effect Of Environment On Survival Ability

Beauveria bassiana BD-B015 showed the highest virulence among our laboratory strains against Laphygma exigua Hubner. BD-B015 strain had the highest sporulation, the highest Protea-Bse activity level, the highest UV radiation viability, and extensive insecticidal spectrum. It had cleared the best liquid culture and solid fermentation conditions, and in order to apply this entomogenous fungi resources in agricultural production, BD-B015 strain was studied deeply, screening the wettable powder formulations, detecting indexes of its preparation, and studying the survival ability in the different soil environment. The results were as the followings.1. BD-B015 conidia were isolated from the liquid-solid two-phase fermentation, the spore powder content was 1.35×1011 spore/g, germination rate was 98.70%, moisture content was are 9.11%,which had reached national standard. Studying on the wettable powder formulations, the suitable carrier of Beauveria bassiana spores powder was kaolinite by analyzing effects of carrier on spore powder germination, growth speed and conidiation, the wetting agent was nekal by analyzing the wetting time and compatibility testing, and the suitable dispersing agent was HK-2302 by compatibility analyzing the dispersing time and compatibility testing. So the preliminary formulations of Beauveria bassiana wettable powder was spore powder 30%, carrier 50%, wetting agent 5%, dispersing agent 5%.2. Beauveria bassiana spores powder, the spore powder content was 400 billion spore/g, the wetting time was 69s, the active ingredient suspension rate was 94.6%, the loss of drying was 1.7%, the fineness was 98.4%, which had achieved national standard. The pot experiment showed that this preparation had a good control to Laphygma exigua Hubner, 96.49% and 81.05% respectively at 100×and 200×dilution after 120h, and had no toxicity against tested crops.3. Studying on the survival ability of Beauveria bassiana spore powder in different soil temperatures, soil moistures, soil textures and microbial existence environment showed that Beauveria bassiana spore powder could survival in different soil conditions, but they had apparent difference. At 25℃, Beauveria bassiana had the highest survival ability in a short time. And high temperature made survival number declined quickly, but Beauveria bassiana maintained at a high level under low temperature in a long term. Lower or higher than 15% soil moisture content were not conducive for survival ability, and the survival number would decline more quickly if the moisture content become higher. Soil microbes could inhibit the growth of Beauveria bassiana at early stage, and Beauveria bassiana could be stimulated at later stage. And Beauveria bassiana had high survival ability in loam than sandy soil.