Organophosphorus insecticides synergize pyrethroids in the resistant strain of cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from West Africa.
Helicoverpa armigera (Hübner) populations from West Africa recently developed resistance to pyrethroid insecticides through enhanced metabolism by mixed-function oxidases. The combination index method was used to study the synergism of pyrethroids by organophosphorus insecticides. Several mixtures of insecticides currently registered to control cotton pest complex in West Africa were tested, including: cypermethrin/ethion, cypermethrin/profenofos, deltamethrin/ triazophos, deltamethrin/chlorpyriphos, cyfluthrin/chlorpyriphos, and betacyfluthrin/chlorpyriphos. In the resistant strain, the organophosphorus insecticides significantly increased the toxicity of pyrethroids suppressing the resistance effect, either by additive or synergistic effects. Significant synergism was shown for the following mixtures: cypermethrin/ethion, deltamethrin/triazophos, and deltamethrin/chlorpyriphos. The use of synergism from these insecticide mixtures should prove to be an additional tool in the overall resistance management strategy because the pyrethroid resistance in H. armigera from West Africa is not yet stable, decreasing between cotton seasons and increasing with treatments. In absence of selection, the susceptibility of H. armigera to insecticides should be restored.
Programme Coton, Centre National de Recherche Agronomique, BP 633 Bouaké Cote D'Ivoire, West Africa.
Thibaud
T
Martin
Ochou G
OG
Ochou
Maurice
M
Vaissayre
Didier
D
Fournier
D000354:Africa, Western; D000818:Animals; D004357:Drug Synergism; D003368:Gossypium; D007305:Insecticide Resistance; D007306:Insecticides / Q000008:administration & dosage*; D009036:Moths; D009943:Organophosphorus Compounds; D011722:Pyrethrins / Q000008:administration & dosage*
D007306:Insecticides; D009943:Organophosphorus Compounds; D011722:Pyrethrins