Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2010
Publication Date: 10/8/2010
Publication URL: http://hdl.handle.net/10113/48461
Citation: Lord, J.C. 2010. Dietary stress increases the susceptibility of Tribolium castaneum to Beauveria bassiana. Journal of Economic Entomology. 103(5):1542-1546. Interpretive Summary: The fungi that are pathogenic for insects provide a safe approach to controlling pests. The insecticidal fungus, Beauveria bassiana, is being considered as non-chemical control for insect pests of stored products including the red flour beetle for which it is less effective than for most insects. Certain stresses on insects render them more susceptible to fungal disease. Restriction of access to food by sanitation is an important stress-inducing means of insect management. Similarly, the nutritional content of various foods is a determinant of insect vigor and success on different commodities. This study investigated the effect of dietary stress on the efficacy of B. bassiana for red flour beetles. When beetle larvae were deprived of food for various periods of time they were more susceptible to fungal infection than when provided a constant food supply. Larvae that were reared on a rice diet were more susceptible than those reared on wheat flour. The addition of protease inhibitors to flour did not increase fungal efficacy, perhaps because of inhibition of fungal proteases by inhibitor residue on insect cuticles. Dietary stress, whether by food deprivation, suboptimal food quality or inhibition of gut digestive proteases significantly affected developmental rate and efficacy of B. bassiana. This research helps to create strategies for non-chemical methods to control insect pests in stored commodities.
Technical Abstract: Sanitation being an important component of chemical-free management of stored-products pests, the nutritional stress that results from a clean environment may prove advantageous to the use of microbial controls. Dietary stress by food deprivation or suboptimal diet increased susceptibility of the red flour beetle, Tribolium castaneum Herbst, larvae to the fungus Beauveria bassiana (Balsamo) Vuillemin. Fungus-related mortality increased linearly with the number of days of food deprivation. Rearing of larvae on a rice meal diet resulted in slower development and greater susceptibility to B. bassiana than rearing on whole wheat flour with brewer’s yeast. Larval rearing in flour with a mixture of protease inhibitors, while slowing development, resulting in smaller larvae and delayed adult emergence than those reared in untreated flour, significantly reduced fungus-associated mortality perhaps due to inhibition of fungus proteases by inhibitor residue on the cuticles.