Author
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Hesler, Louis |
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Dagel, Kurt |
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Submitted to: Great Lakes Entomologist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/10/2010 Publication Date: 11/30/2010 Citation: Hesler, L.S., Dagel, K.J. 2010. Grass hosts of cereal aphids (Hemiptera: Aphididae) between wheat-cropping cycles in South Dakota. Great Lakes Entomologist. 43:1-10. Interpretive Summary: Several grasses may serve as alternative hosts for cereal aphids during the interim between small-grain crops in South Dakota, but field studies to determine which grasses are important have not been undertaken. We sampled annual and perennial grasses for cereal aphids in 18 counties in South Dakota in the month of August over three years. Eighty-five of 240 site samples had one or more species of cereal aphids, including 61 of 65 corn sites and 12 of 13 sorghum and sudangrass sites. Four species of cereal aphids were found during the survey: corn leaf aphid, 74 times; bird cherry-oat aphid, 27 times; greenbug, eight times; and English grain aphid, seven times. Abundance of corn leaf aphid on host plants was rated high seven times, moderate 11 times, and low 50 times, and presence only was noted at six other sites. Abundance of bird cherry-oat aphid was rated high four times, moderate four times, and low 19 times. Abundance of English grain aphid and greenbug was always rated low. All high ratings of corn leaf aphid and of bird cherry-oat aphid occurred on field-corn. Nine moderate ratings for corn leaf aphid and three for bird cherry-oat aphid occurred on corn. Low frequencies of cereal aphids were found on volunteer small-grains and among weedy grass species such as rough barnyard grass, yellow foxtail, and green foxtail. Cereal aphids were not found on other weedy grasses or on noncultivated grasses. The results suggest that corn and, to less degree, sorghum served as predominant grass hosts of cereal aphids during August in South Dakota. Recent trends of expanding corn acreage in South Dakota may potentially lead to concomitant increases of cereal aphids and intensify the risk of fall infestation of winter grains by them. Technical Abstract: Several grasses may serve as alternative hosts for cereal aphids during the interim between small-grain crops in South Dakota, but field studies to determine which grasses are important have not been undertaken. We sampled annual and perennial grasses for cereal aphids in 18 counties in South Dakota in the month of August over three years. Eighty-five of 240 site samples had one or more species of cereal aphids, including 61 of 65 corn sites and 12 of 13 sorghum and sudangrass sites. Four species of cereal aphids were found during the survey: corn leaf aphid, 74 times; bird cherry-oat aphid, 27 times; greenbug, eight times; and English grain aphid, seven times. Abundance of corn leaf aphid on host plants was rated high seven times, moderate 11 times, and low 50 times, and presence only was noted at six other sites. Abundance of bird cherry-oat aphid was rated high four times, moderate four times, and low 19 times. Abundance of English grain aphid and greenbug was always rated low. All high ratings of corn leaf aphid and of bird cherry-oat aphid occurred on field corn. Nine moderate ratings for corn leaf aphid and three for bird cherry-oat aphid occurred on corn. Low frequencies of cereal aphids were found on volunteer small-grains and among weedy grass species such as rough barnyard grass, yellow foxtail, and green foxtail. Cereal aphids were not found on other weedy grasses or on noncultivated grasses. The results suggest that corn and, to less degree, sorghum served as predominant grass hosts of cereal aphids during August in South Dakota. Recent trends of expanding corn acreage in South Dakota may potentially lead to concomitant increases of cereal aphids and intensify the risk of fall infestation of winter grains by cereal aphids. |
