Susceptibility of Classes of Wheat Grown in the United States to Stored-Grain Insects

Abstract

Comparative studies were done on the reproductive rates of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) in relation to physical properties of the predominant U.S. varieties of hard red winter, soft red winter, hard red spring, white, and durum wheats. Reproductive rates of both species differed significantly among the classes, and quantitative data were obtained that may be useful in modeling population growth on the different classes. White wheats were most susceptible to both species, but the ranking of the other classes differed between the two species. Within the classes of wheat, virtually no significant differences between varieties in reproductive rates of either species were apparent. Variation between production sites exceeded that between varieties. Kernel size and density were not suitable criteria for distinguishing between the classes and did not correlate well with reproduction by either species. Kernel hardness differed among the classes and correlated well with S. oryzae reproduction but not with R. dominica. S. oryzae appeared to be sensitive to kernel hardness only when differences were quite large, such as between classes. Small differences in hardness between or within varieties within a class had little effect on S. oryzae reproduction.