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Title: Effects of host nutrition on virulence and fitness of entomopathogenic nematodes: lipid and protein based supplements in Tenebrio molitor diets

Author
item Shapiro Ilan, David
item Rojas, Maria - Guadalupe
item Morales Ramos, Juan
item LEWIS, EDWIN
item TEDDERS, WALKER

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2008
Publication Date: 8/1/2008
Citation: Shapiro Ilan, D.I., Rojas, M.G., Morales Ramos, J.A., Lewis, E.E., Tedders, W.L. 2008. Effects of host nutrition on virulence and fitness of entomopathogenic nematodes: lipid and protein based supplements in Tenebrio molitor diets. Journal of Nematology. 40:13-19.

Interpretive Summary: Beneficial nematodes are small round worms that are natural bio-insecticides. These nematodes kill insect pests but are safe to humans and the environment. One way to grow beneficial nematodes commercially is to infect insects on a mass scale, and harvest the nematodes that come out of these insects. The production method, however, can be limited by excessive costs or by poor quality of nematodes produced. In this study, we have developed technology to improve nematode production by selectively altering the diet of the insects that the nematodes are cultured in. Specifically, we altered the protein or lipid (fat) content of a diet that was fed to the yellow mealworm (an insect commonly used to produce nematodes). After infecting the mealworms fed different diets with nematodes, we found that certain lipid levels can enhance nematode infectivity and thus improve efficiency of production, whereas certain protein levels may decrease the nematodes ability to kill insects.

Technical Abstract: Entomopathogenic nematodes, Heterorhabditis indica and Steinernema riobrave, were tested for virulence and reproductive yield in Tenebrio molitor that were fed wheat bran diets with varying lipid and protein based supplements. Lipid supplements tended to increase T. molitor susceptibility to H. indica whereas susceptibility to S. riobrave was not affected. Protein supplements did not affect host susceptibility, and diet supplements did not affect reproductive capacity of either nematode species. Subsequently, we determined the pest control efficacy of progeny of nematodes that had been reared through T. molitor from different diets against Diaprepes abbreviatus and Otiorhynchus sulcatus. All nematode treatments reduced insect survival relative to the control (water only). Nematodes originating from T. molitor diets with the 20% protein treatment or 0% protein exhibited lower efficacy versus D. abbreviatus than the intermediate level of protein (10%) or bran-only treatments. Nematodes originating from T. molitor lipid or control diets did not differ in their effects on D. abbreviatus or O. sulcatus. Our research indicates that nutritional content of an insect host diet can affect host susceptibility to entomopathogenic nematodes and nematode fitness; therefore, host media could conceivably be optimized to increase in vivo nematode production efficiency. Additionally, our data suggest that insect host diet can impact nematode quality and fitness in laboratory or field trials, and in natural populations.