Red flour beetle, Tribolium castaneum (Herbst), larval development when fed ground and raw dried distiller's grains with solubles at 30 and 50% r.h

Dried Distiller's Grains with Solubles (DDGS), a co-product of ethanol-production process, has high nutrition content and is used in animal feed as a substitute of corn. Due to DDGS high value as a feed ingredient, domestic and international market demand has been dramatically increased during the past few years. As more of DDGS is available to the feed industry, knowledge of the effect it might have on the vulnerability of animal feed to insect infestation is critical for feed safe storage. In fact, US export of DDGS came under scrutiny last year following the discovery of insect pests in a container shipment to Vietnam. The objective of this study was to determine larval development of Tribolium castaneum on different types of ground and raw DDGS compared to flour/yeast (9:1) at 32.5°C and relative humidity (r.h.) of 30 and 50%. Tribolium castaneum larval development at 30 % r.h. was 2-3 times longer on raw DDGS diets with larger particle sizes compared to a flour/yeast diet. However, ground DDGS at 50% r.h. increased DDGS vulnerability to T. castaneum infestation compared to raw DDGS at 30% r.h. Our research has shown that DDGS as a raw ingredient at 30% r.h. is not a suitable food source for T. castaneum and the higher the humidity, the faster the growth of larvae on all diets. We recommend facility managers store DDGS as a raw ingredient with larger particle sizes at r.h. of less than 30%.