Susceptibility of eight US wheat cultivars to infestation by Rhyzopertha dominica (Coleoptera : Bostrichidae)

Cultivars of wheat, Triticum aestivum L., were assessed to determine their respective level of resistance to lesser grain borers, Rhyzopertha dominica (F.) in postharvest storage. Cultivars were representative of hard red win ter, soft red winter, white spring, and durum wheat classes currently grown in the United States. Samples of each cultivar were maintained at 30.0 deg rees C and 70% RH and infested with 2- to 3-wk-old adult beetles for 1 wk. Adult progeny were counted at the end of one life cycle. Two temperatures, 27.0 and 34.0 degrees C, were studied to examine the role of temperature (c alculated in degree-days) in development. This experiment was conducted thr ee times under similar conditions. Cultivars harboring a large quantity of progeny were considered more susceptible than those cultivars in which fewe r progeny completed their life cycle. Each cultivar was analyzed for single kernel properties such as hardness, protein, and diameter. Wheat cultivar had a significant influence on quantity of progeny in all experiments. Ther e were no significant effects on survivorship of progeny as a result of tem perature when calculated in degree-days. Cultivars with smaller kernels wer e more susceptible to development of larger generation sizes in experiment 1 but not in the other two experiments. A kernel size experiment using larg e and small kernels from the same cultivar suggested that larger quantities of progeny are produced on small kernels compared with large kernels. Indi vidual beetle weights were not influenced by temperature or cultivar. These results imply that stored grain managers should be aware of potential diff erences in susceptibility, attributable to wheat cultivar, to lesser grain borer infestations.