Influence of commodity type, percentage of cracked kernels, and wheat class on population growth of stored-product psocids (Psocoptera: Liposcelidae).

Differences in stored-product psocid progeny production as a function of commodity type, percentage of cracked kernels, and wheat class were examined using laboratory bioassays. Population growth of Liposcelis bostrychophila Badonnel, Liposcelis decolor (Pearman), Liposcelis paeta Pearman, and Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae) was highest on sorghum Sorghum bicolor (L.) Moench, followed by wheat, Triticum aestivum L., and rice, Oryza sativa L., whereas progeny production was negligible on wheat germ. In a second experiment that did not include L. entomophila, population growth was examined on wheat containing 0, 1, 5, 10, 20, 50, and 100% cracked kernels. Progeny production did not increase as cracked kernel content increased. Instead, progeny production peaked at 20% for L. bostrychophila adults and nymphs, at 10% for L. decolor, and at 50% for L. paeta adults; no further increases were noted beyond these levels of cracked wheat content. In a third experiment that did not include L. entomophila, progeny production was examined on eight classes of wheat: hard red winter, hard red spring, soft white winter, soft white spring, soft club, durum, soft red winter, and hard white. Overall, progeny production was higher on durum wheat than on the other classes. The results indicate that there are considerable variations in psocid population growth among the different commodities tested, and this information may be used to predict the degree to which stored commodities are susceptible to psocid infestation.