Corn leaf injury from western corn rootworms
On late planted corn, you may notice injury to the leaves that is unfamiliar to you. The leaf may have a "frosted" or dried appearance, particularly along the leaf edge and near the tip. Even though this may appear as some unrecognized plant pathogen, actually what you are seeing is the feeding injury from adult western corn rootworms. When the beetles emerge from the soil, often there are no tassels or silks for the insects to feed on in these late-planted fields. So the beetles will crawl down inside the whorl where they will feed on the tender new leaves. The feeding scars become evident when the leaf eventually emerges and unfurls. The scars run parallel to the leaf veins and may extend 12-15 inches or more along the leaf edge. Occasionally, the beetles will cut through the leaf, which causes long tears in the leaf.