Ovicidal Activity and Alteration of Octopamine Titers: Effects of Selected Insecticides on Eggs of the Tobacco Budworm (Lepidoptera: Noctuidae)

Abstract

The formamidines chlordimeform (CDF), desmethyl-CDF, BTS-27271 (NOR-AM 49844) and amitraz; the pyrethroid lambda-cyhalothrin; and the carbamate thiodicarb were evaluated for ovicidal activity and effects on octopamine titers in eggs of the tobacco budworm, Heliothis virescens (F.). CDF and lambda-cyhalothrin were the most toxic of the compounds examined, followed by desmethyl-CDF and BTS-27271. Although octopamine is not detectable in untreated eggs of H. virescens, three formamidines caused the appearance of octopamine in treated eggs. lambda-cyhalothrin, amitraz, and thiodicarb had no apparent effect on octopamine titers. In vivo metabolism studies of radiolabeled amitraz by eggs of H. virescens indicate that BTS-27271 is a likely metabolite. Because octopamine is involved in insect behavior and energy mobilization, the formamidine-induced alteration of octopamine titers might alter behavioral responses or energy availability during the critical hatching process leading to increased mortality.