Effect Of Environmental Factors On Growth Parameters Of Beauveria Bassiana HFW-05 And Evaluation Of Its Application Efficacy

Beauveria bassiana (Balsamo) Vuillemin is one of the entomopathogenic fungi which applied the most widely presently at home and abroad, to pest control effectively. It could infect more than 700 Species insects of 149 Families in 15 Orders, and caused the epidemic of pests. It had a broad prospect and huge commercial value in biological control. In this paper, the growth and virulence of HFW-05 strain would be studied in different circumstances.By adding 14 Carbon and 11 Nitrogen sources into basis medium, germination rate, growth rate, sporulation and extracellular protease activity of B. bassiana strain HFW-05 were tested. Considering all the index, optimal Carbon and Nitrogen sources were Sucrose and Soybean powerder. The Medium optimization results showed that Carbon sources were the foremost factor of germination, and inorganic salts were suitable for growth rates and sporulation. The best sporulation combination was 4% glycerin +1% yeast extract +0.1% CaCl₂. The results showed that the addition of accessory ingredient could promote germinations of spore. Furthermore, extracellular of HFW-05 strain had positive correlation with its sporulation.To explore sensitivity changes of HFW-05 strain treated by different temperature and ultraviolet irradiation, the growth and toxicity of the strain under different temperature and UV radiation was studied. Results indicated that germination and sporulation of the strain was appropriate at 25℃, and the enzyme production could increase at 30℃. The growth rate and sporulation were increased at 35℃with UV radiation under 1h, but the growth rate would reduce with postponement of the exposure time. The lethal rate of the Plutella xylostella (Linnaeus) was 93.1% by the treatment of 30℃, and it could effectively control the population of insect.The germination rate, growth rate and sporulation of B. bassiana HFW-05 treated by 10 routine insecticides with three dosages of pesticides (Set recommended dosage, one fifth of recommended dosage and tenth of recommended dosage) were assayed in the laboratory. The germination rate of spore reached to 97% at the addition of spinosad, fipronil and pyrethroids could promote the growth of HFW-05 strain. Sporulation of strain was the most with 7.25×10⁸ conidia/cm² in tenth of recommended dosage of Fipronil. Control efficacy of strain mixed with insecticides at the one fifth of recommended concentration was conducted. Corrected mortality of fipronil mixed with strain was up to 98%. Besides phoxim, methomyl and chlorbenzuron, the effect of other mixing manifested better control the population of pest.To evaluate control efficacy of HFW-05 formulation to common pests, HFW-05 formulation was used to control Plutella xylostella (L.) and Bemisia tabaci (Gennadius) in the lab and field respectively. The formulation brought on high mortality of two tested pest in the lab and field. HFW-05 Strain was toxic to the 2 instars larvae of Plutella xylostella (L.) with an LC₅₀ of 8.026×10⁵ conidia/mL, to the 1 instar of Bemisia tabaci (G.) with LC₅₀ of 5.469×10⁶ conidia/mL. The data indicated that LC₅₀ value would be augmentation along with the growth of instar of larvae, and if spore concentration was increased, the effective death rate had also enhanced. Field trials showed that it had better control efficacy with the increasing concentration of formulation and exhibet continued control effect to population of pest. The control efficacy of 5. bassiana with 7.5×10⁷ conidia/mL to Plutella xylostella (L.) and Bemisia tabaci (G.) after 7 days treatment could reach 87.93% and 93.19%, respectively, the pests could be controlled effectively with the concentration in the field.