With soybean aphid infestations, it's important to preserve natural enemies under an integrated pest management approach, as well as treating only when pest populations reach economic or treatment thresholds, to let beneficial insects do their work.
Soybean aphids in Nebraska typically reach the economic threshold and require treatment in late July through August. Treatment during this time is usually enough to keep aphid populations from resurging before they leave fields for the season.
Aphids cause the greatest amount of injury while they are feeding within the whorl prior to tassel emergence. Treatment may be needed if pollination is no more than half complete and more than half of the corn tassels are covered with aphids.