Last July, Joel DeJong, ISU field specialist-crops, and I visited an alfalfa field near LeMars (western Iowa) that had large populations of blackish aphids. This year, Brian Lang, ISU field specialist-crops, reports finding large populations of this dark aphid near Decorah (northeastern Iowa). I suspect that these aphids are cowpea aphids, Aphis craccivora, based on their color.
Iowa State University
Rice, Marlin E., "Cowpea aphids spread across Iowa" (2003). Integrated Crop Management News. 1634.
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