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Soybean aphid infestations are developing: Recommendations for scouting and managing insecticide resistance

by Robert Koch (Extension Entomologist), Bruce Potter (Extension IPM Specialist), Phil Glogoza (Regional Extension Educator)

Scouting for soybean aphids in Minnesota soybean fields should be underway. While aphid populations are low in most fields, we have received reports of increasing soybean aphid numbers. In parts of central Minnesota, some of these fields are nearing threshold levels and will likely require insecticide treatment soon to protect yield. Early-planted soybean in areas with moderate rainfall this year might see significant aphid populations first. However, aphids are now spreading to other fields putting them at risk too. Below, we provide an overview of scouting recommendations and updates on insecticide resistant soybean aphids.

Scouting and threshold:

How will you know if any of your soybean fields are at economic risk from soybean aphid? The decision to apply insecticide for soybean aphid should be based on scouting and the economic threshold. Briefly, you need to get into the field to count or estimate aphid numbers on plants. Count the number of aphids on plants selected from throughout the field. Compare the average number of aphids from those plants to the economic threshold. The economic threshold for soybean aphid is an average of 250 aphids per plant with more than 80 percent of the plants infested with aphids, and the aphid population appearing to be increasing.

See our soybean aphid scouting guide, if you need a refresher on scouting tips and techniques for this pest.

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