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 cracked wheat, Triticum aestivum L. (Gramineae), kernels with sublethal and median-lethal concentrations of Bacillus thuringiensis Berliner 1915 (Eubacteriales: Bacillaceae) on the energy use by Plodia interpunctella (Hübner) 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 sublethal (4 μg/g wheat for P. interpunctella, 250 μg/g wheat for T. castaneum) and median-lethal (18 μg/g wheat for P. interpunctella, 1950 μg/g wheat for T. castaneum) concentrations, food consumption during development decreased from controls by 9.1% and 47.1%, respectively, for P. interpunctella and 14.4% and 38.2%, respectively, for T. castaneum. Egestion decreased by 9.5% and 61.5% for P. interpunctella and 19.4% and 47.3% for T. castaneum at these respective concentrations. Increasing B. thuringiensis had negative effects on food consumption and energy use by the insects. Levels of B. thuringiensis lower than required for complete control may assist in protecting grain from stored-product insects.