Mechanisms of Pyrethroid Resistance in Larvae and Adults from a Cypermethrin-Selected Strain of Heliothis virescens (F.)

• Published in: Pesticide biochemistry and physiology Vol. 66; no. 1; pp. 20 - 32
• Main Authors: Ottea, J.A., Ibrahim, S.A., Younis, A.M., Young, R.J.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.01.2000; Elsevier
• Subjects: Biological and medical sciences; Chemical control; Control; cypermethrin; Fundamental and applied biological sciences. Psychology; Heliothis virescens; Insecta; Noctuidae; Phytopathology. Animal pests. Plant and forest protection; Protozoa. Invertebrates; pyrethroids; Heliothis virescens; Insecticide; Insecta; Pesticides; Pyrethroids; Metabolism; Pest; Sensitivity resistance; Penetration; Larva; Arthropoda; Cypermethrin; Lepidoptera; Adult animal; Selection pressure; Developmental stage; Noctuidae; Pesticide resistance; Invertebrata
• ISSN: 0048-3575; 1095-9939
• DOI: 10.1006/pest.1999.2448

Mechanisms of pyrethroid resistance were measured in larval and adult tobacco budworms, Heliothis virescens (F.), from laboratory strains that were selected either as larvae or as adults for 9 generations with cypermethrin. Regardless of the life stage treated, selection resulted in cypermethrin resistance in both larvae and adults, which was associated with reduced rates of penetration and increased metabolism of cypermethrin. Levels of resistance were higher in adults (45- to 70-fold) than in larvae (8.5- to 12-fold) after 9 generations of selection. Decreased penetration was detected following selection in both larvae and adults but differences between selected and unselected insects were not dramatic. Resistance in the two life stages was highly correlated (r2 >0.85) with cypermethrin metabolism, as measured from extracts of excreta and carcasses of insects treated with radiolabeled cypermethrin. In contrast, results from in vitro assays using model substrates for P450-monooxygenase, esterase, and glutathione S-transferase activities were not correlated with resistance (or with metabolism measured in pharmacokinetic assays), suggesting that activities toward these model substrates were poor markers for cypermethrin metabolism and resistance. Target-site sensitivity to pyrethroids was measured in larvae (but not adults) from both colonies. Decreased sensitivity was detected in larvae from selected colonies, although frequencies of expression did not increase dramatically after 5 generations of selection.