Research On Beauveria Bassiana Formulations And Applicaiton Technology For Thrips Control

Western flower thrips, Frankliniella occidentalis Pergande is an important invasive pest insect in China.Onion thrips, Thrips tabaci Lindeman is a world important pest. Thrips not only make direct damage to vegetable crops by feeding, but also transmit dangerous virus. The loss caused by thrips is serious. However, with the increase of thrips' insecticide resistance, the public pay much more attention to biological control. Beauveria bassiana, an important biological agent, plays an important role in biological control of thrips. The writer regarded Western flower thrips and Onion thrips as research objects. The pathogenicity of isolates of entomopathogenic fungus Beauveria bassiana to adult WFT, was tested under laboratory conditions. The isolates selected were screened for their virulence against WFT adults at higher temperatures and for their conidia production characteristics. The formulations of Beauveria bassiana suspension emulsion and dry Beauveria bassiana suspension emulsion was screened under laboratory conditions. The control effect of Beauveria bassiana suspension emulsion to onion thrips, was tested under field conditions. The major results and conclusions are listed as follows:The pathogenicity of isolates of entomopathogenic fungus Beauveria bassiana to adult WFT, was tested under laboratory conditions. The isolates selected were screened for their virulence against WFT adults at higher temperatures and for their conidia production characteristics. Results showed that: thermal tolerance, isolate SZ-26outperforms with the shortest LT50(30℃, LT50=1.561d;34℃, LT50=2.607d) and the highest mortality rate(30℃,98.56%;34℃,95.31%) within10days at30℃and34℃. The yields of isolate SZ-26conidia powder and the number of isolate SZ-26efficient conidia is significantly more than other selected isolates. The results indicate that the isolate SZ-26has great potential to control F. occidentalis in field in an integrated management program as a biological agent.Based on original Beauveria bassiana suspension emulsion formulation, We further optimized this formulation and screened the type and dosage of emulsifier, dispersant and thickener. Result showed that:the best Beauveria bassiana suspension emulsion formulation consisits of3.5%emulsifier B,8.1%oil B,1%dispersant C,0.065%thickener B,0.1%ascorbic acid,2%conidia powder,85.235%distilled water. And the indices of suspension emulsion formulation selected were tested under laboratory conditions. The formulation is stable emulsion with ivory. Water layer is below0.1%. There is no precipitation. It is very well in dispersity. Suspended rate is93.56%. pH value is6. viscosity is0.25Pa· s. Microtherm stability is good. And the formulation has good compatibility with conidia. Germination rate is up to92.4%. The screening of Beauveria bassiana suspension emulsion formulation prepared for that of Beauveria bassiana dry suspension emulsion formulation.On basis of the ingredient of Beauveria bassiana suspension emulsion formulation, Beauveria bassiana dry suspension emulsion formulation was further improved in the first time. The ways of crush and solution was also screened. We detected the quality indice of formulation, phytotoxicity situation in field and storage period. Results showed that the best Beauveria bassiana dry suspension emulsion formulation consisits of3.5%emulsifier B,8.1%oil B,1%dispersant C,0.065%thickener B,0.1% ascorbic acid,2%conidia powder,0.00162%antioxidant,85.233%water-soluble packing. The best way of crush is that Beauveria bassiana dry suspension emulsion is crushed by high-speed smashing machines for2min and repeated3times. The best way of solution is that Beauveria bassiana dry suspension emulsion is dissolved and grinded by glass rob. And the indices of dry suspension emulsion formulation selected were tested under laboratory conditions. The sate of dry suspension emulsion formulation is loose powder particles. The fineness (through40eye test-screen) is96.39%. The water content is2.36%. The suspended rate of solid effective component is94.71%. pH is7. It shows very well in dispersity. And the formulation has good compatibility with conidia. Moreover, The phytotoxicity situation of the formulation in field was tested. Results showed that In certain condition(Average temperature is23.5℃, average humidity is70.2%), the dry suspension emulsion formulation sprayed in field concentration1X107conidia· ml-1) was not harmful to seedings tested(tomato, kidney bean, cucumber, pepper, cotton, turnip). The storage period of formulation was also tested. Result shows that after3months'storage in25℃, the germination rate of formulation declined to70.13%. While after5months'storage in5℃, the germination rate declined to69.93%. We first did research on the ingredients of Beauveria bassiana dry suspension emulsion, which has great significance to conquer the storage problem of entomopathogenic fungi formulation.In May and November,2011, Beauveria bassiana suspension emulsion formulation was sprayed to control onion thrips in greenhouse. In spring trial, result showed that the relative control efficacy of suspension emulsion formulation to adult onion thrips is up to86.98%after7day's application and to larva onion thrips is up to63.24%after3day's application. In autumn trial, result showed that:the relative control efficacy of suspension emulsion formulation to adult onion thrips is up to69.81%after7day's application. The two field trials shows that Beauveria bassiana suspension emulsion formulation has good control efficacy against onion thrips.