D3031: Evaluating variation of sorghum protein contents on Rhyzopertha dominica L. (Coleoptera: Bostrichidae) and Sitophilus oryzae L. (Coleoptera: Curculionidae) development

Sorghum (Sorghum bicolor) is a cereal grain that varies widely in kernel size, color, hardness, and grain composition based on variety and growing conditions. Our objective was to evaluate the developmental effects of sorghum protein content from multiple sorghum varieties grown in Kansas on two primary stored product pests: Rhyzopertha dominica (L.) and Sitophilus oryzae (L.). We classified 19 different sorghum varieties, into low (9.1-9.9g/100g), medium (10.2-11.5g/100g), and high (11.9-13.2) protein content via nitrogen combustion analysis using a LECO FP 828P nitrogen and protein analyzer. Each species was assigned 3 varieties in each category and the lab sorghum diet was used as a control (n=10). Ten adults from either species were placed on 40 g of each variety in 0.12-L vials and were incubated at 27°C and 60% r.h.  for 7 d. Adults were removed after 7 d, assessed for mortality, and vials held for 8 wks. Three reps from each variety, each with 5 sub-reps, for a total of 15 reps per sorghum variety were tested. During storage, sub-samples were taken weekly and x-rayed to monitor insect development. After 8 wks, vials were analyzed for adult progeny, weight of frass and brokens, insect damaged kernels (IDKs), and % weight loss.  Preliminary data for R. dominica trials have indicated a significant relationship between protein content and the % weight loss of samples, which indicates that sorghum grain with higher protein contents could be more susceptible to product loss due to infestation.