Temperature Stratification and Insect Pest Populations in Stored Wheat with Suction versus Pressure Aeration

Abstract

<abstract> <b><i>Abstract. </i></b> A three-year study was conducted to compare temperature profiles in the headspace and in the bulk mass of wheat aerated through pressure aeration and suction aeration. Insect pitfall traps were used to measure naturally-occurring populations of stored product insects. Results show uniform distribution of temperatures in the headspace until the area immediately above the top of the grain mass. In general, suction aeration cooled the top portion of the grain mass more quickly than pressure aeration, based on measured temperatures, days above specified temperature thresholds, and total heat accumulations above those thresholds, for each of the three years. Populations of (Stephens), the rusty grain beetle, and Herbst, the red flour beetle, were generally at least 2x to 4x greater in pressure versus suction aeration, depending on the specific sampling date, during the first two years of the study. An extensive infestation that developed during the third year may have diminished the effects of aeration. The other two insect species caught in abundance were two fungus-feeding insects, (L.), the hairy fungus beetle, and (Waltl), the foreign grain beetle. Mixed effects were observed for these two species under the two aeration treatments. Results show that suction aeration may be preferable over pressure aeration, but afternoon temperatures lead to a buildup of heat in the headspace that affected the temperature of the upper layer of the grain mass. Installing a thermostat for controlled aeration utilizing the headspace temperatures as a set point instead of relying on outside ambient temperatures may increase efficiency of suction aeration.