Seasonal Variation of Stored Wheat Environment and Insect Populations

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Abstract
Temperatures of wheat in the top meter in on-farm cylindrical metal bins in Kansas were uniform and within a favorable range of 27–34°C for the first 12 wk and then declined at rates ranging from 1.3 to 2°C/wk. Cooling of grain from the outside and surface inward and downward resulted in temperature gradients. Grain moisture in the top 0.5 m declined during the first 12 wk and then increased to levels well above initial moisture. Elsewhere in the top meter, wheat retained its initial moisture level except for the tendency of grain near the bin wall to be drier. Population growth rate of the dominant species, Cryptolestes ferrugineus (Stephens), declined over the wheat storage period in the top meter of grain as a result of first the parasite Cephalonomia waterstoni Gahan and then falling temperatures. C. ferrugineus adults showed only a slight tendency to move toward the warmer or moister parts of the bin. Trogoderma glahrum (Herbst) adults and larvae and Trogoderma inclusum LeConte adults, the next most abundant species, were found mainly near the bin wall. Rhyzopertha dominica (F.) were first detected after 12 wk and were found only in the center.