Lethal Activity of a Trehalase Inhibitor, Validoxylamine A, against Mamestra brassicae and Spodoptera litura

Abstract

Relaxation of the larval segmental muscles was elicited soon after injection of validoxyl-amine A (VAA) into the larvae of the cabbage armyworm, Mamestra brassicae, and the tobacco cutworm, Spodoptera litura. Mortal abnormalities, i.e. extrusion of the gut from the anus, failure of pupation and incomplete pupation occurred only at later stages. LD50 values of VAA were less than 1 μg/larva and 2.42 μg/larva in Mamestra and Spodoptera, respectively. Activity of VAA was markedly reduced when VAA was applied topically (LD50 was more than 50 μg/larva in both species), and oral administration of 50 μg/larva had no effect. Relaxation of the segmental muscles seems to be caused by blocking the energy source, trehalose, through trehalase inhibition by VAA. However, how trehalase inhibition causes the abnor-malities at later stages remains unclear. © 1994, Pesticide Science Society of Japan. All rights reserved.