The cross-resistance of DDVP-resistant and cypermethrin-resistant strains of Culex pipiens pallens to the common chemical pesticides
Objective To investigate the cross-resistance of Culex pipiens pallens to common pesticidesso as to provide a basis for the rational use of chemical pesticides.Methods The sensitivity of sensitive,dichlorvos (DDVP)-resistant and cypermethrin-resistant strains of Culex pipiens pallens Ⅳ instar larvae to six common chemical pesticides (acetofenate,DDVP,malathion,propoxur,cypermethrin and deltamethrin) was detected based on WHO bioassay method.Seven concentrations were set up for each experiment.Two groups were set up for each concentration and each group had 25 larvae.The dead larvae were detected after 24 h exposure.The median lethal concentration (LC50),regression equations and resistance indices were then calculated.Results The LC50 of DDVP-resistant strain of Culex pipiens pallens to acetofenate,DDVP,malathion,propoxur,eypermethrin and deltamethrin were 1.962 3 mg/L,1.160 7 mg/L 0.735 9 mg/L,0.900 2 mg/L,0.022 0 mg/L and 0.000 1 mg/L respectively.And the regression equations for them were Y=3.528 7+ 5.025 4X,Y=4.696 2+4.693 7X,Y=5.505 1+3.853 6X,Y=5.235 0+5.147 6X,Y=10.499 5+3.318 4X and Y=13.297 7+2.168 3Xrespectively.The resistance indices for them were 9.25,12.17,9.14,7.93,183.47 and 0.71respectively.The LC50 of cypermethrin-resistant strain of Culex pipiens pallens to acetofenate,DDVP,malathion,propoxur,cypermethrin and deltamethrin were 5.572 8 mg/L,0.246 4 mg/L,0.089 2 mg/L,0.202 7 mg/L,0.064 1 mg/L and 0.008 5 mg/Lrespectively.The regression equations for them were Y=2.772 8+2.985 2X,Y=7.205 4+3.626 0X,Y=9.475 1+4.263 5X,Y=6.810 6+2.612 5X,Y=8.740 4+3.135 2X and Y=14.695 1+4.685 3X respectively.The resistance indices for them were 26.27,2.58,1.10,1.79,534.31 and 40.60 respectively.Conclusion Mosquito will generate resistance when using one kind of chemical pesticide in a long time.It will also generate different levels of cross-resistance to other pesticides.So when using chemical pesticides,we should take measures such as rationally selecting chemical pesticides and determining the appropriate dose of chemical pesticides to avoid generating the resistance of mosquito to the chemical pesticides.
NETL
NSTL
万方数据
维普
