This study did not give an indication of economic threshold levels or optimum timing of aphid control. Rather, they suck sap from the leaf vascular system. This results in increased plant stress and stunting. Many heavily infested fields in 2000 also showed signs of potassium deficiency. Viral diseases apparently contribute to yield losses where heavy insect infestations occur.
Colonies concentrate on new terminal trifoliolate leaves and new leaves on side branches.
Given our inexperience with the soybean aphid, it's difficult to predict how much of a problem we will have during the upcoming growing season. The aphid overwintering host is common buckthorn. There is an abundance of this plant growing both in the wild and as an ornamental. To what extent the soybean aphid survives a Wisconsin winter is yet to be determined. The educated guess is that they will survive unless conditions are extremely harsh.