Effect of Bacillus thuringiensis on feeding and energy use by Plodia interpunctella (Lepidoptera : Pyralidae) and Tribolium castaneum (Coleoptera : Tenebrionidae)

Investigations were conducted to quantify the effects of treatment of crack ed wheat, Triticum aestivum L. (Gramineae), kernels with sublethal and medi an-lethal concentrations of Bacillus thuringiensis Berliner 1915 (Eubacteri ales: Bacillaceae) on the energy use by Plodia interpunctella (Hubner) 1813 and Tribolium castaneum (Herbst) 1797 larvae. Cumulative food consumption and egestion during insect development and the weight and energy values of adult insects were determined and oxygen consumption was estimated. At subl ethal (4 mu g/g wheat for P. interpunctella, 250 mu g/g wheat for T. castan eum) and median-lethal (18 mu g/g wheat for P. interpunctella, 1950 mu g/g wheat for T. castaneum) concentrations, food consumption during development decreased from controls by 9.1% and 47.1%, respectively, for P. interpunct ella and 14.4% and 38.2%, respectively, for T. castaneum. Egestion decrease d by 9.5% and 61.5% for P. interpunctella and 19.4% and 47.3% for T. castan eum at these respective concentrations. Increasing B. thuringiensis had neg ative effects on food consumption and energy use by the insects. Levels of B. thuringiensis lower than required for complete control may assist in pro tecting grain from stored-product insects.