Adult beetles impact grain fill by chewing off the green silks, causing spotty pollination later in the season. The larval stage, however, is the most damaging and impacts yield by feeding on corn roots. One way to determine the current level of rootworm pressure and the potential for future threats is to scout your fields for adult beetles in July and August. Scouting helps determine whether to spray the current crop and limit the potential for population outbreaks the next crop season. When scouting, look for lodged plants with heavy damage on the root system.
To ensure that spraying rootworm beetles will pay off, determine that the critical population threshold has been met before using an insecticide. This guideline is location specific, so consult your local DuPont Pioneer agronomist or Pioneer sales professional for corn rootworm beetle threshold levels in your area. If the threshold is met, apply timely foliar insecticides to control the egg-laying adult population.