University of Minnesota Southwest Research and Outreach Center, Lamberton
Before anyone gets too bent out of shape over this... Yes, I know this is a stressful time for some soybean growers, most of their advisers and for aphid researchers too. It is not illegal to apply insecticide to any population of soybean aphids as long as it is within label restrictions. Finally, I am not the police and it's the soybean farmer's money, not mine, at risk. Insecticide resistance does tend to spread itself around though.
Based on emails and phone calls, there seem to be several economic (action) thresholds for soybean aphids in use now.