ENHANCEMENT OF ACTIVITY OF BACILLUS-THURINGIENSIS BERLINER AGAINST 4 LEPIDOPTEROUS INSECT PESTS BY NUTRIENT-BASED PHAGOSTIMULANTS

To help improve control of insect pests with microbial insecticides, w e investigated the interactions of four commercial, nutrient-based pha gostimulants (Pheast [AgriSense], Coax [CCT Corp.], Gusto [Atochem Nor th America, Inc.], and Entice [Custom Chemicides] with Bacillus thurin giensis Berliner and four lepidopterous insect posts (gypsy moth, Lyma ntria dispar [L.] [Lymantriidae]; corn earworm, Helicoverpa zea [Boddi e] [Noctuidae]; European corn borer, Ostrinia nubilalis [Hubner] [Pyra lidae]; and diamondback moth, Plutella xylostella [L.] [Plutellidae]). Comparisons were made of treated foliage in Petri dishes in the labor atory and of sprayed whole plants in a greenhouse. In general, phagost imulants increased mortality of all species tested, but no consistent differences among phagostimulants were found for any species. Food con sumption was generally lower on the treatments that contained phagosti mulants causing the highest rates of mortality, possibly as a result o f more rapid ingestion of a lethal dose on these treatments. Reduced r ates of feeding by insects on treatments with B. thuringiensis alone w ere seen, probably due in part to intoxication and, possibly, to behav ioral effects as well. Indications of potentially significant interact ions between host plants and both B. thuringiensis and phagostimulants also were seen.