昆虫病原线虫与Bt联用对黏虫的防治效果

为明确昆虫病原线虫与Bt联用后对黏虫致病力的协同增效作用, 本研究分别测定了自主分离获得的一种新嗜菌异小杆属线虫Heterorhabditis sp.(LF)和实验室保存的Heterorhabditis bacteriophora(Hb)线虫对黏虫的致病力; 比较了两种Bt菌株(HD1和G03)对黏虫的毒力差异, 开展了G03对黏虫的毒力测定试验; 明确了室内和田间试验条件下两种线虫(LF和Hb)与G03联用对黏虫的交互作用。结果表明, 黏虫的死亡率随两种线虫剂量的增加而增加, 在100 IJs/mL剂量下黏虫死亡率均达到了90%以上; Bt菌株G03对黏虫的毒力显著高于HD1, G03对黏虫的LC50为3.55×10 10 cfu/mL; 室内条件下LF 25 IJs/mL+G03(LC50)联用处理6 d对黏虫的防治具有显著的协同增效作用, 较单独LF线虫和G03处理死亡率分别提高了50.72和50.0百分点, Hb 25 IJs/mL+G03(LC50)联用处理6 d对黏虫的防治也具有显著的协同增效作用, 较单独Hb线虫和G03处理死亡率分别提高了76.67和50.0百分点; 田间小区试验表明线虫与Bt联用对黏虫的防治具有协同的加成或增效作用, 其中LF线虫与G03联用具有显著的增效作用, 较单独LF线虫和Bt处理死亡率分别提高了47.96和46.80百分点。本研究为黏虫的防治提供了新的技术措施, 拓宽了黏虫生防研究的思路。

Control efficacy of the combined application of the entomopathogenic nematode and Bt against the oriental armyworm, Mythimna separata (Walker)

In this study, we examined possible synergistic effects resulted from a combined application of the entomopathogenic nematode and Bt based on their virulence against Mythimna separata. The virulence of a newly isolated nematode Heterorhabditis sp. (LF) and a laboratory-maintained nematode Heterorhabditis bacteriophora (Hb) against Mythimna separata was determined and the virulence of two Bt strains (HD1 and G03) against M.separata was compared. The interactive effect of two nematodes (LF and Hb) and G03 on M.separata was determined under both laboratory and field conditions. The results showed that the mortality of M.separata increased with the dose of two nematodes. The mortality of M.separata reached more than 90% when 100 IJs/mL was applied. The LC50 value of of Bt strain G03 was 3.55×10 10 cfu/mL, significantly higher than that of HD1. Compared to single application of nematode or Bt, combined application exhibited a significant synergistic effect. The mortality of M.separata increased by 50.72% and 50.0% when LF 25 IJs/mL+G03 (LC50) was applied for 6 days under indoor conditions, respectively. The application of Hb 25 IJs/mL+G03 (LC50) exhibited a significant synergistic effect of 76.67% and 50.0% under indoor conditions after 6 days compared to the controls (Hb or G03 applied alone), respectively. Field trials showed that a combined application of nematodes and Bt had additive or synergistic effects on the mortality of M.separata. The combination of LF nematode and G03 showed a significant synergistic effect of 47.96% and 46.80%, respectively, higher than nematodes and Bt when applied alone. This study not only provides a new technical measure for the prevention and control of M.separata but also expands the research scope of biological control of M.separata.