Food Consumption by Heliothis zea (Lepidoptera: Noctuidae) Larvae Intoxicated with a β-exotoxin of Bacillus thuringiensis

Abstract

A β-exotoxin of Bacillus thuringiensis Berliner was tested against fourth-instar Heliothis zea (Boddie) to determine its impact on ability of larvae to feed. Fourth-instar H. zea were fed diet treated with 0.0, 25.0, 35.0, 50.0, and 100.0 μg of β-exotoxin per milliliter of diet. Upon molting, larvae were transferred to untreated peanut leaves and consumption (square centimeters) was measured during the fifth stadium. Intoxication by each, β-exotoxin concentration caused a significant reduction in mean total leaf consumption that decreased exponentially with increased concentration. In each treatment group, the majority of total leaf area consumed was eaten by those larvae that survived intoxication. However, mean total leaf consumption by treated survivors was significantly less than that by untreated larvae and decreased with increasing β-exotoxin concentration. Many treated larvae experienced a prolongation of their fifth stadium, but their mean total leaf consumption was also significantly less than that by untreated cohorts.