关键词: 芫菁夜蛾斯氏线虫SF-SN')">芫菁夜蛾斯氏线虫SF-SN, 噻虫嗪')">噻虫嗪, 韭菜迟眼蕈蚊')">韭菜迟眼蕈蚊, 杀虫效果')">杀虫效果, 搜寻效应')">搜寻效应

Abstract: 【Aim】 After the entomopathogenic nematodes (EPN) are exposed to chemical pesticides, their potential bioefficacy and searching effect on insect pests might change. This study aims to investigate the bioefficacy and searching effect of entomopathogenic nematodes treated with thiamethoxam on Bradysia odoriphaga larvae. 【Methods】 The lethal and searching effects of S. feltiae SF-SN strain (Sf) treated with thiamethoxam (15 mg/L) on the 3rd instar larvae of B. odoriphaga were tested under laboratory conditions using a filter-paper culture method, and the differences in the functional responses and searching effect between the thiamethoxam-treated Sf and the untreated Sf were evaluated. 【Results】 The corrected mortality of B. odoriphaga larvae exposed to thiamethoxam-treated Sf was significantly higher than that exposed to the untreated Sf, and was increased by 2.13 times as compared with that exposed to the untreated Sf at 6 h post treatment. When the concentration of Sf was 6 400 IJs/petri dish, the functional responses for killing action of untreated and thiamethoxam-treated Sf on the 3rd instar larvae of B. odoriphaga could be described by Holling’s type II and Ⅲ disc equation. The attack rate (a′=0.5592) of thiamethoxam-treated Sf increased by 42.76%, the handling time (T_h=0.0081 d) (the cumulative time taken in searching, parasitizing and killing the host) decreased by 44.90%, the consumption rate (a′/T_h) increased by 2.59 times, and the daily maximum lethal amount (Na_max) increased by 1.81 (Holling’s type II) and 1.41 (Holling’s type III) times, respectively, as compared with those of the untreated Sf. The searching effect of both untreated and thiamethoxam-treated Sf decreased with increasing larval density of B. odoriphaga. When the larval density of B. odoriphaga was 40 per petri dish, the lethal effect of thiamethoxam-treated and untreated Sf increased with increasing Sf concentrations, while the searching effect first increased and then decreased. The searching parameter and mutual interference parameter of thiamethoxam-treated Sf were higher than those of the untreated Sf. 【Conclusion】 The corrected mortality of B. odoriphaga larvae and the attack rate, consumption rate, daily maximum lethal amount and searching effect of thiamethoxam-treated Sf on B. odoriphaga larvae are higher than those of the untreated Sf, while the handling time is shorter than that of the untreated Sf.

Key words: -SN')">Steinernema feltiae SF-SN, thiamethoxam, Bradysia odoriphaga, bioefficacy, searching effect