Journal of Medical Entomology (2007) 44, 822-829

Shinji Kasai, Toshio Shono, Osamu Komagata, Yoshio Tsuda, Mutsuo Kobayashi, Mitsugu Motoki, Ichiro Kashima, Tsutomu Tanikawa, Masahiro Yoshida, Ikuo Tanaka, Goro Shinjo, Tomoyuki Hashimoto, T. Ishikawa, T. Takahashi, Y. Higa and T. Tomita (2007)
Insecticide resistance in potential vector mosquitoes for West Nile virus in Japan
Journal of Medical Entomology 44 (5), 822-829
Abstract: Culex pipiens complex is the significant vector mosquito of West Nile virus. To take stock of the current situation of insecticide susceptibilities and design an ideal mosquito control strategy, we collected Culex pipiens pallens Coquillet, Culex pipiens form molestus Forskal, and Culex quinquefasciatus Say from fields in Japan and conducted bioassays for five larvicides (fenitrothion, temephos, etofenprox, diflubenzuron, and pyriproxyfen) by using a larval dipping method. Among five insecticides tested, obvious reduced susceptibilities were observed for etofenprox, which is the only pyrethroid compound registered as a larvicide in Japan. Twenty-two of 56 colonies exhibited a >10% survival rate at the etofenprox concentration of 5.7 μg/ml, which is a 10 times higher concentration of the working solution. The LC₅₀ of a colony collected from Fukuoka prefecture for etofenprox exceeded 60 μg/ml (resistance ratio >2,307), and this colony also exhibited cross-resistance to other pyrethroids, permethrin (299-fold) and phenothrin (1,200-fold). The insect growth regulators diflubenzuron and pyriproxyfen were found to be sufficiently effective enough to control Culex larvae present, but decreased sensitivities to these insecticides were slightly detected in some colonies of Cx. p. form molestus collected from urban areas. Several etofenprox-resistant colonies of Cx. p. form molestus exhibited simultaneously decreased susceptibilities to other insecticides, including temephos, diflubenzuron, and pyriproxyfen.
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Database assignments for author(s): Shinji Kasai, Mutsuo Kobayashi, Takashi Tomita, Yoshio Tsuda

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Culex quinquefasciatus		Japan
	Culex molestus		Japan
	Culex pallens		Japan