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 (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. Micro-bioassays examined effects of extracts on living larvae. Cell culture assays examined effects of the seed extracts on H. zea cells. Midgut enzyme inhibition assays examined the potential of the extracts to disrupt H. zea larval digestive processes. These three assays showed that P. macroloba seeds contain factors that retard H. zea growth, reduce the viability of H. zea 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 seeds have approximate molecular weights greater than or equal to 3,500 and are heat-labile. Results from recovery studies indicated that H. zea larvae have a limited ability to overcome the toxic effects of the active water-soluble components of P. macroloba seeds