Insecticide susceptibility of Culex pipiens pallens (L.) and Aedes albopictus (Skuke) to five commonly used pesticides in the Republic of Korea

Field collected populations of two mosquito species, Culex pipiens pallens and Aedes albopictus, were tested for susceptibility to five pyrethroid insecticides using a topical application bioassay. The laboratory strain of Cx. pipiens pallens (KS-CP) demonstrated the most and the lowest susceptibility to deltamethrin and d-cis/trans prallethrine with LD50 values of 0.00022 mu g/female and 0.00178 mu g/female, respectively, while Ae. albopictus (KS-AL) showed the greatest and the lowest susceptibility to phthalethrin and deltamethrin with LD50 values of 0.00015 mu g/female and 0.00085 mu g/female, respectively. Cx. pipiens pallens (JF-CP) collected at a nearby rice field in Jeonju showed the greatest susceptibility to deltamethrin (LD50 value of 0.0473 mu g/female) and the resistance ratios (RRs) and compared to the laboratory strain were 215 fold greater. JF-CP demonstrated the lowest susceptibility to d-cis/trans phenothrin (0.7697 mu g/female) with RRs 711.0 fold greater than the KS-CP. An Ae. albopictus (JF-AL) collected at a nearby forest in Jeonju showed the highest susceptibility to deltamethrin (0.00203 mu g/female) with RRs 2.4 fold greater than the KS-AL. JF-AL demonstrated the lowest susceptibility to d-cis/trans prallethrine (LD50 value 0.00646 mu g/female) with RRs 9.4 fold greater than the KS-AL. JF-AL demonstrated the greatest resistance to phthalethrin with RRs 39.3 fold greater than the KS-AL. Resistance ratios of Cx. pipiens pallens between field and laboratory strains ranged from 215.0 to 711.0 and Ae. albopictus ranged from 2.4 to 39.3. These results indicate that the choice of effective insecticides to selected species of mosquito populations will result in more effective control against field strains of mosquito vectors and decrease environmental pollution.