At greatest risk and generally with the greatest numbers of aphids per plant are those fields where there is buckthorn habitat nearby or other wooded areas that have provided a wind buffer during aphid migration from buckthorn. These sites had good colonization of aphids along the border areas. Smaller fields were readily colonized by aphids across the entire field, while larger fields have generally declining aphid numbers as you move away from those borders.

Aphid populations are growing rapidly under the current weather conditions. The optimum temperatures for soybean aphid development and reproduction is between 77˚and 86˚F (figure 1). Guess where our maximum and minimum temperatures have been fluctuating the past two weeks? The range for Min-Max temperatures has been from 56˚- 82˚ F in our region.

Soybean aphid are entering a migration phase in their summer cycle. Plants that have the larger populations are beginning to produce many alatoid nymphs, or nymphs with wing buds (figure 2). While scouting fields, it is becoming very easy to find migrating winged adults as the only aphids present on the plant. Typically, the winged adults land on plants, give birth to a few live aphids, and then move on to another plant.

Applications of insecticides have begun in the region. In some cases, applications are warranted; treatments are premature in other cases. Some premature decisions to treat are being made because of scheduled/needed glyphosate applications.