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Esterase-mediated resistance to pyrethroids in field populations of Helicoverpa armigera (Lepidoptera: Noctuidae) from Central Africa

Achaleke J., Martin T., Ghogomu R.T., Vaissayre M., Brévault T.. 2009. Pest Management Science, 65 (10) : p. 1147-1154.

DOI: 10.1002/ps.1807

BACKGROUND: Evolution of pyrethroid resistance in the cotton bollworm Helicoverpa armigera (H ¨ ubner) (Lepidoptera: Noctuidae) threatens continued cotton production in Central Africa. Dose-response bioassays were conducted on areawide collection of bollworm populations from major host plants, while biochemical techniques were used to evaluate basic mechanisms underlying resistance. RESULTS: Pyrethroid resistance is primarily associated with detoxification by enhanced esterase activity. High resistance to cypermethrin (RF = 67-1771), cross-resistance to deltamethrin (RF = 60-2972) and lack of cross-resistance to the non-ester pyrethroid etofenprox (RF = 2-10) were observed among H. armigera field populations and laboratory-selected strains. Enzymatic assays showed that esterase activity, but not oxidase content or glutathione-S-transferase activity, was positively correlated with resistance to cypermethrin. Pretreatment with piperonyl butoxide (PBO) resulted in significant synergism with cypermethrin in 6/10 field populations, but not in the laboratory-selected strain, indicating that additional mechanisms such as mixed-function oxidase (MFO) may be involved in field resistance. The absence of cross-resistance to DDT ruled out a possible target-sitemodification. CONCLUSION: Knowledge of the mechanisms involved in pyrethroid resistance and the lack of cross-resistance to spinosad and indoxacarb is a key to devising new resistance management strategies aimed at restoring the efficacy of pyrethroid-based programmes.

Mots-clés : gossypium; helicoverpa armigera; pyréthrine; insecticide; estérase; résistance aux pesticides; expérimentation; cameroun; tchad; pyréthroïde

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