Comparison of dose responses and resistance ratios in four populations of the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), to 20 insecticides.
BACKGROUND
Chemical control is a major strategy for suppressing the rice stem borer, Chilo suppressalis (Walker). Owing to their high toxicity and increasing resistance development in the target insect, many insecticides will be phased out entirely in 2007 in China. Alternatives with relatively low toxicity are urgently needed to replace traditional chemicals for rice stem borer control. In this study, the authors examined four field populations of C. suppressalis for their toxicological responses to more than 20 insecticides, including a few low-toxicity organophosphates and many novel pesticides. Interpopulation resistance levels to 12 conventional insecticides were also compared.


RESULTS
Based on LD(50) values, the rice stem borer was most sensitive to avermectins and fipronil (LD(50) < 1 ng larva(-1)). The stem borers exhibited the least sensitivity to endosulfan (LD(50) > 100 ng larva(-1)) and monosultap (LD(50) > 1000 ng larva(-1)). Insect growth regulators and chitin synthase inhibitors showed great efficacy against C. suppressalis, especially against populations that had developed resistance to conventional insecticides. Four field populations showed variable tolerance levels to many insecticides. LYG05 was the most susceptible population, only with a low level of resistance to monosultap (RR = 6.6). NC05 and GL05 populations exhibited intermediate tolerance levels with RR values up to 20.4 and 52.8 respectively. RA05 was the most resistant population to many insecticides, with resistance ratios up to 76.2.


CONCLUSIONS
The results from this study provide valuable information for selection and adoption of new alternative insecticides and for resistance management of the rice stem borer.
He
Yue Ping
YP
Department of Pesticide Science, College of Plant Protection, Nanjing Agriculture University, Nanjing 210095, China.
Gao
Cong Fen
CF
Chen
Wen Ming
WM
Huang
Li Qin
LQ
Zhou
Wei Jun
WJ
Liu
Xu Gan
XG
Shen
Jin Liang
JL
Zhu
Yu Cheng
YC
D000818:Animals; D001681:Biological Assay; D002681:China; D004305:Dose-Response Relationship, Drug; D007305:Insecticide Resistance; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D009036:Moths / Q000187:drug effects*
D007306:Insecticides