噻虫嗪对昆虫病原线虫侵染韭菜迟眼蕈蚊能力的影响

【目的】为提高昆虫病原线虫对韭菜迟眼蕈蚊Bradysia odoriphaga Yang et Zhang幼虫的防治效果,将昆虫病原线虫与环境友好型化学杀虫剂混用是一条有效途径。【方法】测定了噻虫嗪与6个昆虫病原线虫品系混用对韭菜迟眼蕈蚊的作用效果,以及温度和土壤含水量对作用效果的影响,并进行了田间验证。【结果】田间推荐浓度噻虫嗪(100 mg·L~(-1))对6种供试线虫存活无显著影响。处理后3 d,低浓度噻虫嗪(15 mg·L~(-1))分别与6品系线虫混合后处理韭菜迟眼蕈蚊幼虫,其死亡率明显高于线虫和噻虫嗪单用处理。小卷蛾斯氏线虫SF-SN+噻虫嗪、印度异小杆线虫LN2+噻虫嗪和小卷蛾斯氏线虫All+噻虫嗪3种组合发挥杀虫作用的最适温度范围分别为20~25℃、25~30℃和25~30℃,显著高于其他温度;最适土壤含水量范围为10%~18%,也显著高于其他湿度。大田条件下,施用后7 d,单用噻虫嗪、线虫+噻虫嗪组合处理对韭菜迟眼蕈蚊的防治效果显著高于单线虫,且以芫菁夜蛾斯氏线虫SF-SN+噻虫嗪的防治效果最高,达到93%以上。【结论】芫菁夜蛾斯氏线虫SF-SN品系与噻虫嗪组合联合防治韭菜迟眼蕈蚊效果最好。

Evaluation of the effects of infection by different entomopathogenic nematodes and thiamethoxam on Bradysia odoriphaga

Objectives] To increase the effectiveness of controlling Bradysia odoriphaga with entomopathogenic nematodes, and to screen pesticides as synergists for entomopathogenenic nematodes. Methods] The survival rate and infectivity of six entomopathogenic nematodes (Steinernema carpocapsae NC116, S. carpocapsae All, S. longicaudum X-7, S. feltiae SF-SN, Heterorhabditis bacteriophora H06 and H. indica LN2) were tested after dipping them in a commonly used pesticide (25%water dispersible granules of thiamethoxam). The effects of treatment with six nematodes and low concentrations of thiamethoxam (12 mg·L-1) on 3rd instar larvae were determined. Interactions between three kinds of nematodes (S. feltiae SF-SN, H. indica LN2 and S. carpocapsae All), and low concentrations of thiamethoxam (30 mg·L-1), were evaluated under various temperature and humidity conditions and further tested under greenhouse conditions. Results] The recommended concentration of thiamethoxam (100 mg·L-1) had no effect on nematode survival. Mortality of B. odoriphaga treated with a combination of six nematodes and a low concentration thiamethoxam (12 mg·L-1) was higher after 3 d than that of larvae that had been treated with thiamethoxam and any one nematode. Mortality of B. odoriphaga treated with S. feltiae SF-SN+thiamethoxam, H. indica LN2+thiamethoxam and S. carpocapsae All+thiamethoxam was higher at 20-25℃, 25-30℃, and 25-30℃, respectively, than at other temperatures. The optimum substrate moisture level for these treatments was 10%-18%. The results of greenhouse trials show that a combination treatment (S. feltiae SF-SN+thiamethoxam) achieved>93%better control than treatment with thiamethoxam (100 mg×a.i./L) alone after 7 d. Conclusion] The S. feltiae SF-SN+thiamethoxam combination appears an effective way of controlling B. odoriphaga.