Common-used Insecticide Resistance Of Culex Tritaeniorhynchus In Different Populations And The Preliminary Resistance Mechanism Research

Culex tritaeniorhynchus is the main vector of epidemic encephalitis B, the control of it is an important part to reduce the incidence of epidemic encephalitis B. Chemical control is the most commonly used method in mosquitoes control strategy. Along with the use of pesticides and under the long-term selection pressure of the insecticides, Mosquito will develop resistance to the widly used pesticides and are becoming more and more serious. Recent years, Cx tritaeniorhynchus pesticides resistant studies have focused on the larvae, adult resistance level surveillance and the resistance mechanism research has rarely been reported. Aim to provide evidence for Cx tritaeniorhynchu control and the resistant management, there is an urgent need for the study of different geographic Cx tritaeniorhynchus populations’resistance levels and resistance mechanisms.We collected Cx tritaeniorhynchus in Wanzhou, Yongcheng and Licheng and evaluated insecticide resistance using the World Health Organization(WHO) recommended resistance monitoring method and got the resistant levels to five kinds of pyrethroid pesticides(deltamethrin, cypermethrin, cypermethrin, permethrin and tetramethrin); four kinds of organic phosphorus(fenitrothion, Temephos, DDVP and malathion); BPMC, propoxur carbamate and DDT; we use the F1larvae in Licheng population as the test insects to study the synergistic effect of synergists on it’s resistance to temephos; in this study we also tested the esterase specific activities of four populations (Wanzhou, Licheng, Shanxi, Yunnan), try to get a preliminary understanding of their insecticide resistance mechanisms. The results are as follows:1. Three different Cx tritaeniorhynchus populations’resistance levels to five kinds of pyrethroids were high, with the characteristics of regional differences. Resistance levels in Wanzhou and Yongcheng populations are higher than that in the Licheng population; the larvae of Licheng populations are relatively sensitive to deltamethrin, cypermethrin, permethrin.2. The resistance levels of three different populations to fenitrothion, propoxur, DDT were very high. After the contacting time, the mortality of Wanzhou, Licheng populations to fenitrothion(2h) were (3.08±0.1)%and (16.1±2.1)%, to propoxur (2h)(59.2±14.0)%and (16.9±4.7)%, to DDT(4h)(87.7±0.1)%and (36.4±8.4)%. The mortality of Yongcheng population to DDT(4h) was35.64%. The larvae of Licheng population had developed high resistance to DDVP, fenitrothion, malathion, temephos, with76.6,256.5,84.2,7977.8folds respectively compared to the sensitive baseline, the resistance to temephos has the highest resistance ratio.3. Use the piperonyl butoxide (PBO), triphenyl phosphate (TPP) and maleic acid diethyl ester (DEM) as synergist,3:1mixed with temephos, among the Licheng Cx tritaeniorhynchus population, they all showed synergistic effect to temephos. The result showed that when we want to control the larval of Cx tritaeniorhynchus using temephos, synergist can be used simultaneously to improve the mosquito control.4. Three different geographical populations of Cx tritaeniorhynchus esterase enzyme activity assay showed that different populations have different esterase enzyme activities, this differences may be related to the different pesticides resistance level; the esterase enzyme activity also relate to the developmental stages.