| Aschersonia placenta is a classic entomogenous fungus to control whiteflies, which is widely popular for microbial pest management in agriculture and forestry sytems. However, mass production and wide application of Aschersonia in our country have never been recorded up to now. Intensive studies on manufacturing techniques of Aschersonia must be conducted before it's produced on a large scale and applied abroadly. Determination of Aschersonia resistance, screening of low-cost and highly efficient natural media for sporulation, and development of fungal emulstfiable suspension were performed in this study, which facilated to commercialize and apply the fungus.Effects of Carbon Sources, Nitrogen Sources, Metal Ions and Vitamins on development of Entomogeous funguns Aschersonia placentaAmong 19 carbon sources, glucose, trehalose and D-fructose were the best C source for germination, growth and spore production, respectively. For ten nitrogen sources, yeast powder, yeast extract and glycine was the best N source for germination, growth and sporulation as well, respectively. No significant effects of metal ions and vitamins on the spore germination, mycelial growth and sporulation were observed in the test, except for Fe2+ on sporulation with a little function.Resistance of Aschersonia placenta to temperature and UVHeat and cold are environmental abiotic factors that restrict the use of entomopathogenic fungi as agents for biological control of insects. The thermotolerance and UV tolerance of A. placenta were examined in the test and the results showed that 26℃was the optimal temperature for growth, fungal conidia were extremely low thermotolerant. The conidia were totally inactivated after exposure at 32℃... The tests indicated that the isolate was cold-active and the conidia still formed colonies at 4℃... The approximate median lethal temperature (LT50) after 2h exposure for Aschersonia isolate was 34℃. and conidia suspension was very sensitive to ultraviolet light, the spores were almost entirely inactivated after 1 min exposure.UV has little effect on germination, after germination at 26℃for 8 h, the ralative culturability was more than 87%.Screening of natural medium for sporulationTo determine the best cultural medium for Aschersonia placenta conidiation, 12 cm Petri dish was taken as an example, 150 g corn flour was added into per 1000ml water to form medium, 1ml spore suspension with concentration of 1×106 spores / ml was used to inoculated on the medium, the general medium weight at around 80 g.The effect of sugars on fungus spore production is not significant.The formula of emulstfiable suspensionThree commonly emulsifiers used in food were choosed for screening the suitable conidia emulsifier. In addition to sodium dodecyl sulfate, the other agents could show compatibility with the spores well. General emulsification, compatibility and other physical and chemical traits, 0.2% sucrose fatty acid ester SE-11 as emulsifier, 0.3% carboxymethyl cellulose as stabilizer and 0.2% ascorbic acid for ultraviolet protective agent, which were best combination for the formula of emulstfiable suspension.Bioassay of Aschersonia placenta conidia emulstfiable suspensionBemisia tabaci mortality rate was at about 25℃and 90%RH. However, only 20% mortality rate was observed in the outdoors.
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