Western corn rootworm, Diabrotica virgifera virgifera, adults are numerous in most of Illinois. We have reports of their covering outside building walls, swarming golf courses, and creating piles of dead beetles on beaches.
These adult beetles are about 1/4 inch long and yellow to pale green, with three black stripes down the back. The underside is yellowish. On males, the anterior area of the wing covers isblack, whereas females have more distinct stripes.
Although rootworms are the most important pest of corn in Illinois, the adults are primarily a nuisance in landscapes. Little can be done about them. When present in large numbers on buildings, they can be killed on contact with insecticidal soap. Applications may need to be made daily. Insecticidal soap is un-likely to harm foundation plantings, although other soaps are likely to damage foliage and roots.