Pentaclethra macroloba Seed Effect on Larval Growth, Cell Viability, and Midgut Enzyme Activity of Helicoverpa zea (Lepidoptera: Noctuidae)

Tests were conducted to determine whether seeds from the tropical plant Pentaclethra macroloba</it> (C.L. Willdenow) O. Kuntze contain factors that retard or inhibit growth of larvae of Helicoverpa zea (Boddie). Three different assays were used to determine effects of aqueous seed extracts on H. zea</it>. Micro-bioassays examined effects of extracts on living larvae. Cell culture assays examined effects of the seed extracts on H. zea</it> cells. Midgut enzyme inhibition assays examined the potential of the extracts to disrupt H. zea</it> larval digestive processes. These three assays showed that P. macroloba</it> seeds contain factors that retard H. zea</it> growth, reduce the viability of H. zea</it> cells, and specifically inhibit the activity of trypsin and chymotrypsin proteinases from the larval midgut. In addition, dialysis and heat treatment indicated that the active, water-soluble factors in P. macroloba</it> seeds have approximate molecular weights ≥3,500 and are heat-labile. Results from recovery studies indicated that H. zea</it> larvae have a limited ability to overcome the toxic effects of the active water-soluble components of P. macroloba</it> seeds.