Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2009
Publication Date: 10/1/2009
Citation: Nansen, C., Flinn, P.W., Hagstrum, D.W., Toews, M.D., Meikle, W.G. 2009. Interspecific Associations Among Stored-Grain Beetles. Journal of Stored Products Research. 45: 254-260. Interpretive Summary: Insects reduce the quality of stored grain and other stored products in the U.S. and throughout the world. Many laboratory studies have described interspecific relationships of stored grain insects, but little is known about such relationships under field conditions. Using data collected from a total of 1,118 wheat samples in Kansas grain elevators, the interspecific relationships between the three most common insect pests of stored wheat were studied. We found that these three beetle species significantly affected each other. The rusty grain beetle was more evenly distributed than the lesser grain borer, and high numbers of either the rusty grain beetle or the red flour beetle may have adversely affected the numbers of lesser grain borer; this may have been due to cannibalism. The findings from this study will be used to improve existing models of insect population dynamics in stored grain, which will lead to improved insect pest management programs for stored grain.
Technical Abstract: Many laboratory studies have described interspecific relationships of stored grain insects, but little is known about such relationships under field conditions. Compared to most other habitats, natural or man-made, a loaded grain silo constitutes a uniquely uniform habitat in which food availability is unlimited. For this reason, insect data from grain silos can be used to address a very basic question – to what extent are interspecific relationships of insects density-dependent when food availability is unlimited? A total of 1118 wheat samples collected in 1999-2001 from grain silos in Kansas were used to examine interspecific relationships among three important stored grain beetle species: Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), Cryptolestes ferrugineus Stephens (Coleoptera: Laemophloeidae), and Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). Individual beetles species appeared to be spatially aggregated particularly along vertical gradients in the grain mass, densities of the three beetle species appeared to significantly affect each other, and the nature of these relationships were density-dependent. Cryptolestes ferrugineus was more evenly distributed than R. dominica and T. castaneum was intermediate, and high numbers of C. ferrugineus and/or T. castaneum may have adversely affected the numbers of R. dominica. This study suggests that, especially at high beetle densities, interspecific relationships are probably quite important. Using simple linear and quadratic coefficients from response surface regression analyses, we demonstrated that interspecific relationships among three important stored grain beetle species could be characterized as density-dependent (i.e. the effects of both C. ferrugineus and T. castaneum on R. dominica), while other relationships did not appear to be markedly density-dependent within the examined density range (i.e. the effect of R. dominica on both C. ferrugineus and T. castaneum).