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Contributions of Monooxygenases and Esterases to Pyrethroid Resistance in the Tobacco Budworm, Heliothis Virescens

Guomin Shan and Jim Ottea


An in vitro assay was used to measure the metabolism of cypermethrin in homogenates of pyrethroid-susceptible and -resistant tobacco budworms. Total metabolism was greater in field-collected and laboratory-resistant larvae compared to that in a laboratory-susceptible strain. In addition, metabolsim of cypermethrin was greater in a late- than early-season collection. These results confirm that enhanced metabolism is associated with pyrethroid resistance in this insect. Three metabolites were identified from homogenates of resistant larvae: phenoxybenzoic acid, phenoxybenzyl alcohol and 4'-HO-cypermethrin. Phenoxybenzoic acid was the predominant metabolite produced in crude homogenates from all strains suggesting that hydrolysis of cypermethrin by esterases plays a key role in resistance in these strains.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 1148 - 1151
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998