| Chilo suppressalis is one of the most important pests on rice,which seriously endangers the yield and quality of rice in China.The characteristics of the cockroaches and the transgenic plants have made it difficult to control.The country is vigorously advocating green prevention and control,so chemical pesticide control can no longer meet the needs of control.Therefore,the development of new entomogenous fungi and biological pesticides is of great significance for exploring the green prevention and control technologies for C.suppressalis.In this paper,the isolation and identification of entomogenous fungi;entomogenous fungi and biopesticides were used to determine the virulence of the 2nd instar larvae of C.suppressalis,and the strains and biopesticides with high virulence were screened;the compatibility of highly virulent strains with biopesticides.The effects of high-virulence strains and biopesticides on egg mass and larva of C.suppressalis were systematically evaluated.The application effect of C.suppressalis provides a theoretical basis for the biological control of C.suppressalis.The main results obtained from the experiment are as follows.1、The entomogenous fungi’s isolation,purification and systematic identification.To isolate the fungi from natural diseased Myzus persicae(Sulzer)aphids,which was collected from tobacco field were systematically identified.The 8 strains were identified as Verticillium lecanii by biological characteristics observation,ITS sequence alignment and construction of phylogenetic tree.8 strains’ sporulation on the 15th day was significantly different(F7,17=521.40,P=0.00),strain V4 has the highest sporulation(1.89×109/dish),and the fastest growth rate which reached 68.78±0.35 mm at 15 days.The strain V8 could protrude on L-broth、SDAY and PDA medium while other strains don’t.Alignment by ITS sequences,strain V3 is closely related with Torrubiella in evolution which may be sexual.2、Screening of High virulence strains and Biopesticide of C.suppressalis larvaeThe C.suppressalis larvae of the 2nd instar larvae were used as the research object.8 strains of V lecanii identified,16 strains of Beauveria bassiana and 5 biopesticide were screened highly virulent strains and biopesticide for the same temperature and humidity by impregnation method.The results showed that different strains and biopesticide had different virulence to the 2nd instar larvae of C.suppressalis.Only strain V3 showed strong virulence in the V.lecanii group.The cumulative corrected mortality rate reached 50.0%of V.lecanii strain V3 on the 10th day after infesting C.suppressalis larvae,while the cumulative corrected mortality rate of the other round branches on the 10th day was lower than 34.0%,showing significant difference.The cumulative corrected mortality rate reached 53.6%of Bb05 on the 5th day,and the cumulative corrected mortality rate reached 85.2%of Bbl on the 10th day after infecting C.suppressalis larvae,which was significantly higher than that of other B.bassiana.Among the biopesticide,the cumulative corrected mortality was 93.2%on the 10th day,and the pathogenicity was the strongest in Empedobacter brevi.Based on the above experimental results,strains V3,Bb05,B1,and biopesticide Empedobacter brevi were screened for the next experiment.3.Determination of compatibility between high virulence strains and BiopesticideThe compatibility is mainly to determine whether the pesticide can inhibit the spore germination rate of fungi,mycelium growth and other indicators to explain whether fungi and pesticides can be mixed.The results showed that there was no significant difference in the spore germination rate and the mycelial growth rate on the 10th day of the strains cultured with Empedobacter brevi in the medium and strains not cultured with Empedobacter brevi in the culture medium.The spores germination and hyphal growth of the strain were not inhibited by Empedobacter brevi.There was a good compatibility between the strains with high virulence and Empedobacter Brevi.4、Synergistic effects of high virulence strains and biopesticide on egg mass and larva of C.suppressalisFrom the experimental results,the combination of Empedobacter brevi and highly virulent strains has a great influence on the hatching of eggs and the number of larvae zombie.The hatching rate of the V3 group was 91.41%,which was significantly reduced to 7.76%after the addition of Empedobacter brevi.The larval zombie rate of Bb05 group was 10.40%,and that of Bb05+ Empedobacter brevi was significantly reduced to 6.31%.Empedobacter brevi with high virulence strains cooperate to deal with 2nd instar larva.B1+Empedobacter brevi group,Bb05+Empedobacter brevi group,V3+Empedobacter brevi group cumulative corrected mortality rate reached 100.0%on the 5th,6th and 9th day,and LT50 were 3.2 d,3.8 d,4.1 d.However,the LT50 of B1 group,Bb05 group,V3 group,Empedobacter brevi group were 6.3 d,5.1 d,8.4 d,5.8 d.LT50 was significantly shortened.The results showed that the virulence of the highly virulent strains was improved by cooperating with bio-pesticides,and the synergetic effect was very good. |
