Insects infesting barley stored on farms in Minnesota

Barley stored on farms in Minnesota in 12 storage facilities during 1985 and 17 facilities during 1986 was sampled for adults of insect species. Grain samples were removed with grain probing devices or a plastic scoop, and live insects were trapped with unbaited plastic probe traps. Analysis of grain and probe trap samples indicated that, on average, about 85.0 to 100.0% of the facilities holding barley were infested with more than one insect species. The insect species most commonly occurring in grain or probe trap samples were Cryptolestes spp.; red flour beetle, Tribolium castaneum (Herbst); sawtoothed grain beetle, Oryzaephilus surinamensis (L.); foreign grain beetle, Ahasverus advena (Waltl); lesser grain borer, Rhyzopertha dominica (F.); and hairy fungus beetle, Typhaea stercorea (L.). Cryptolestes spp. and O. surinamensis were the most abundant insect species. Indianmeal moth, Plodia interpunctella (Hubner), larvae or adults were rarely found in the grain or probe trap samples, although adult males were captured in pheromone traps that were placed above the grain. Temperature of the grain in July and August 1985 and grain samples between May and September 1986 was within the range (15.6 to 35.0 degrees C) conducive for insect survival and reproduction. Moisture content of the grain samples during 1985 ranged from 12.0 to 16.0% and from 11.0 to 20.0% in 1986. These moisture levels were adequate to support insect infestations. Moisture content of the grain samples during 1985 and 1986 decreased by approximately 0.1 and 0.2%, respectively, for every 1 degrees C rise in grain temperature between 7 and 35 degrees C. Based on test weight of the grain samples, 5 of 12 facilities during 1985 and 3 of 17 facilities during 1986 held poor quality barley (U.S. Sample Grade). The amount of dockage in the grain samples ranged from 0.0 to 4.6%. Comparison of probe traps and grain sampling devices indicated that probe traps were more sensitive than a deep-bin cup probe, a grain trier, or a plastic scoop in detecting adults of insect species that feed on broken or damaged barley kernels and dockage or mold on kernels.