›› 2018, Vol. 61 ›› Issue (7): 851-859.doi: 10.16380/j.kcxb.2018.07.012

• RESEARCH PAPERS • Previous Articles     Next Articles

Bioefficacy of the combined application of entomopathogenic nematodes and thiamethoxam and its effects on the protective and detoxification enzyme activities in Bradysia odoriphaga (Diptera: Sciaridae) larvae

WU Hai-Bin1, GONG Qing-Tao1, CHEN Zhen-Zhen2, JIANG Li-Li1, GONG Yi3, XU Yong-Yu2, SUN Rui-Hong1,*    

  1. (1. Shandong Institute of Pomology, Tai′an, Shandong 271000, China; 2. College of Plant Protection, Shandong Agricultural University, Tai′an, Shandong 271018, China; 3. Shandong Plant Protection Station, Jinan 250100, China)
  • Online:2018-07-20 Published:2018-07-20

Abstract: 【Aim】 Pathogenic organisms or chemical pesticides can induce the defense responses of insects, and the physiological adaptation of insects might differ under the combined application of pathogenic organisms and chemical pesticides. This study aims to investigate the effects of combined application of entomopathogenic nematodes and thiamethoxam on Bradysia odoriphaga. 【Methods】 The LT50 value of the combined application of Steinernema feltiae SF-SN strain (Sf) (60 IJs/larva) and thiamethoxam (15 mg/L) against the 3rd instar larvae of B. odoriphaga was determined with filter paper culture method in the laboratory, and its effects on the protein content of enzyme solution and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferases (GSTs) and acetylcholinesterase (AChE) in B. odoriphaga larvae at different time after treatment were assayed by biochemical analysis. 【Results】 The LT50 value (41.05 h) of the combined application of Sf and thiamethoxam against the 3rd instar larvae of B. odoriphaga decreased by about 126.88 h and 31.77 h, respectively, as compared with those in treatments with the respective single agents with (Sf LT50: 167.93 h) and thiamethoxam (LT50: 72.82 h). During 24-72 h after treatment, the corrected mortality rates of B. odoriphaga larvae in the combined treatment group were significantly higher than those in treatments with the respective single agent, and reached the peak (96.61%) at 72 h. The protein contents of enzyme solution in B. odoriphaga larvae in the combined treatment group at 12, 24 and 36 h after treatment increased by 13.88%, 46.87% and 57.99%, respectively, as compared with the control group, and were significantly higher than those in the control group, Sf treatment group and thiamethoxam treatment group. The activities of SOD, CAT, AChE and GTSs in larvae in the combined treatment group decreased by 47.48%, 28.73%, 71.04% and 29.97% at 24 h after treatment, and by 46.34%, 4222%, 58.37% and 11.87% at 36 h, respectively, as compared with the control. The activities of the four enzymes in the combined treatment group were significantly lower than those in the control group, Sf treatment group and thiamethoxam treatment group at 24 h and 36 h after treatment. 【Conclusion】 The LT50 value of the combined application of Sf and thiamethoxam against the 3rd instar larvae of B. odoriphaga is significantly lower than those in treatments with the respective single agent, and the combined treatment can significantly restrain the activities of SOD, CAT, AChE and GTSs in larvae.

Key words: Bradysia odoriphaga, entomopathogenic nematode, Steinernema feltiae SF-SN, thiamethoxam, enzyme activity