Kevin Black with Cargill, Inc., found winged corn leaf aphids in the whorls of corn plants across a wide area in the northern half of Illinois during the week of June 26. The presence of winged aphids suggests that they might have been recently blown into Illinois on the storm fronts that have passed through. Winged aphids (adults) also mark the potential beginning of the buildup of colonies. We usually associate large numbers of corn leaf aphids with droughty conditions, which certainly do not exist in most areas of Illinois. However, if the water were to shut off tomorrow, corn leaf aphids are capable of increasing their numbers dramatically. So keep your eyes on them. |
Corn leaf aphids and cast skins.
Winged corn leaf aphids are about 1/16 inch long with clear wings and black eyes, thorax, and legs. The abdomen is pale blue-green with black spots on each side and with lighter, transverse black bands. Two black cornicles ("tailpipes") are evident at the rear of the abdomen. The base of each cornicle is surrounded by a black spot. Adult wingless corn leaf aphids are blue-green and 1/16 to 3/32 inch long. The cornicles, bases of cornicles, and legs are black.
If corn plants have adequate moisture, corn leaf aphids cause little damage. However, feeding by aphids during drought conditions exaggerates symptoms of drought stress. Watch for colonies of corn leaf aphids as tassels begin to emerge and pollination begins. And keep us posted.--Kevin Steffey