[Comparative action of 31 insecticides on chlorpyrifos-sensitive and resistant Culex pipiens (L.) larvae in the South of France].

In urban and sub-urban areas larval populations of Culex pipiens are now resistant to chlorpyrifos. A replacement compound must be found so 31 pesticides were tested against 3 strains: 2 of them were bred in the laboratory (on sensitive and one resistant) and the third one collected in an area treated with agricultural pesticides and chlorpyrifos. The results show that this last compound induces a cross-resistance only to organophosphorus compounds especially to parathion, chlorpyrifos-methyl, pyrimiphos-methyl, diazinon and Abate. Agricultural pesticides made this species resistant to chlorinated hydrocarbon and organophosphorus compounds. Among the latest, trichlorfon, azinphos-methyl, methidathion and malathion are still efficient as are propoxur, Decis (pyrethroid), methoprene and Dimilin.