苏云金芽孢杆菌对黏虫致病力及生长发育的影响

Effects of Bacillus thuringiensis on pathogenicity and growing develop-ment of Mythimna separata(Walker)

黏虫[Mythimna separata(Walker)]作为一种易爆发成灾的迁飞性害虫,是我国危害最重的粮食害虫之一。采用生物测定方法,测定9株苏云金芽孢杆菌(Bacillus thuringiensis,Bt)菌株对黏虫致病力,筛选出一株对黏虫具有较高致病力菌株Bt46。该菌株对1龄幼虫致病力最弱,对2龄幼虫致病力最强,致死中浓度LC_(50)为5.25×10^(6)芽孢·mL^(-1),在1×10^(8)芽孢·mL^(-1)浓度2龄幼虫24 h校正死亡率达81.08%,96 h达100%。菌株Bt46对黏虫成虫具有致病性,其致死中浓度LC_(50)为4.66×10^(8)芽孢·mL^(-1),1×10^(10)芽孢·mL^(-1)处理成虫168 h校正死亡率达80.77%。该菌株半致死浓度处理黏虫对黏虫生长发育产生不利影响,处理幼虫虽对当代存活群体生长发育影响较小,但后代卵孵化率显著降低;处理成虫,其寿命显著缩短、产卵量减少约2/3,后代1龄幼虫死亡率达24.29%。研究结果为Bt在黏虫生物防治中应用提供理论和试验证据,有助于推动黏虫绿色防控技术发展。

As a species of migratory pest,Mythimna separata(Walker)is prone to outbreak,and it is one of the most harmful grain pests in China.In this paper,the pathogenicity of nine Bacillus thuringiensis(Bt)strains to M.separata was determined by bioassay,and a strain Bt46 with high pathogenicity to M.separata was screened.The strain had the weakest pathogenicity to the 1st instar larvae.The strongest pathogenicity to the 2nd instar larvae,and the median lethal concentration(LC_(50))was 5.25×10^(6) spores·mL^(-1),the adjusted mortality rate of the 2nd instar larvae at 1×10^(8) spore·mL^(-1) concentration reached 81.08%at 24 h and 100%at 96 h.The strain Bt46 had pathogenicity to adults of M.separata,and its LC_(50) was 4.66×10^(8) spores·mL^(-1),the corrected mortality of adults treated with 1×10^(10) spores·mL^(-1) for 168 h was 80.77%.The results showed that the median lethal concentration of the strain had a negative effect on the growth and development of M.separata.Although the larvae treated by this strain had little effect on the growth and development of the contemporary survival population,the hatching rate of the offspring eggs was significantly reduced.After treated with the strain,the life span of the adults was significantly shortened,the number of eggs laid was reduced by about 2/3,and the mortality of the first instar larvae was 24.29%.The results provide theoretical basis and experimental evidence for the application of Bt in biological control of M.separata,and help to promote the development of green control technology of M.separata.