| In the period of 2001-2004, the study was carried out in Fujian academy of forestry, Yunxiao county, Hui'an county and Guangzhe county. Three excellent strains of Beauveria bassiana against dendrolimus punciatus, notodontidae in populus euramericana and monochamus alternatus were screened out from seventeen strains of Bb, which preserved in the laboratory and collected from yield. By magnification, the screened super strains were used to control in forest with different formulations and fungus application amount. At the same time, we investigated ecological diversity in pinus massoniana stand, where was ultra-low-volume spraying of oil formulation of Bb. The main conclusions are given as follow:Because natural body with many competed moulds caused trouble to isolate, five fungistasis such as CuSO4, Crystal violet, Chloramphenicol, Dacotech WP and Kocide WP were used to screened purer strains of Bb. The selective medium had high selection for Bb, which consisted of the following ingredients per litre distilled water: potato 200 g, glucose 20 g, fine peptone 10 g, agar 20 g, CuSO4 1 g. Use of the selective medium could increase efficiency of isolation and purify of Bb, which increased from 5.4 to 11.1 colony of Bb and decrease from 2.7 to 10.1 colony of competed moulds, and growth rate of the mycelium of Bb in it had 1.28 times as PDA culture medium.The seventeen strains of Bb were tested on colony morphology, growth rate of mycelium, sporulation, spore germination rate and virulence. The results showed that threescreened excellent strains named Byx, Bjy, Bma13 were the best on other characters, which lawns were chick, colonies were round, edges were regular, thickness were uniform and veins were clear. Firstly, the screening strain from dendrolimus punctatus in Yunxiao county had excellent characters, which sporulation is 3.78 X 10s per square centimeter and spore germination rate is 97.24% within twenty-four hours. The toxicity determination showed that the mortality reached 97.8% and white cadaver rate was 95.5% on the twentieth day, and control in forest with twenty powders per 0.667 hectare indicated that white cadaver rate was more than 80% on the fifteenth day and the mortality reached 96.1% on the thirtieth day. Secondly, the screening strain from notodontidae in populus euramericana in Guangzhe county had excellent characters, which sporulation is 3.81 X108 per square centimeter and spore germination rate is 96.67% within twenty-four hours. The toxicity determination showed that the mortality reached 94.4% and white cadaver rate was 92.2% on the twentieth day, and control in forest with powders indicated that white cadaver rate was more than 80% on the fifteenth day and the mortality reached 90.7% on the thirtieth day. Lastly, the screening strain from monochamus alternatus in Wuyi city had excellent characters, which sporulation is 3.23 X 108 per square centimeter and spore germination rate is 41.6% on eighteenth hours in nutrient solution. The toxicity determination showed that white cadaver rate was 100% against monochamus alternatus. Therefore, they would have a significant protective effect on the controlling stands where had less pests, and they could be widely put into use.The spore germination rate can directly affect on the possibility of host being parasited, because the more rapidly the spore germinated, the higher probability of host were parasited, at the same time, the spore germination rate is a index of the vigor of the strain. Under the condition of more than 95% relative humidity and from 25 C to 28 C, the spore germination rate reached more than 84.6% and mortality rate accelerated with LT50was below 4.84 days, however, the spore germination rate reduced that was the spore apparently decreased pathogeny of pine caterpillar when relative humidity was below 95%, or temperature was above 28 C and below 25 C. Therefore, controlling of Bb in forest should be performed after raining or in the morning in Spring or Winter.The forms of oil formulation, emulsion, water agent and powder o...
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