LETHAL ACTIVITY OF A TREHALASE INHIBITOR, VALIDOXYLAMINE-A, AGAINST MAMESTRA-BRASSICAE AND SPODOPTERA-LITURA

Relaxation of the larvral segmental muscles was elicited soon after in jection of validoxylamine A (VAA) into the larvae of the cabbage armyw orm, Mamestra brassicae, and the tobacco cutworm, Spodoptera litura. M ortal abnormalities, i.e. extrusion of the gut from the anus, failure of pupation and incomplete pupation occurred only at later stages. LD5 0 values of VAA were less than 1 mug/larva and 2.42 mug/larva in Mames tra and Spodoptera, respectively. Activity of VAA was markedly reduced when VAA was applied topically (LD50 was more than 50 mug/larva in bo th species), and oral administration of 50 mug/larva had no effect. Re laxation of the segmental muscles seems to be caused by blocking the e nergy source, trehalose, through trehalase inhibition by VAA. However, how trehalase inhibition causes the abnormalities at later stages rem ains unclear.