Resistance of field-collected populations of Culex pipiens pallens (Diptera: Culicidae) to insecticides in the Republic of Korea

Abstract

Toxicities of 10 insecticides were examined against late third instars of Culex pipiens pallens, the northern house mosquito, using a direct-contact mortality bioassay. Several strains of mosquitoes were tested (insecticide-susceptible KS-CP strain and five geospatially distant field-collected strains (DG-CP, US-CP, BS-CP, GS-CP, and SG-CP)) and identified by polymerase chain reaction. Marked regional variations of insecticide susceptibility were observed. Extremely high to low levels of resistance were measured: bifenthrin, resistance ratio (RR) = 1–521; β-cyfluthrin, RR = 16–397; α-cypermethrin, RR = 9–343; deltamethrin, RR = 1–40; etofenprox, RR = 2–42; permethrin, RR = 3–46; chlorpyrifos, RR = 2–675; fenitrothion, RR = 0.5–364; and fenthion, RR = 2–360. All strains were susceptible to one or more of the insecticides examined. These results indicate that careful selection and rotational use of these insecticides may result in continued satisfactory control against field populations of northern house mosquitoes.