Potato Stem Borer and Hopvine Borer
Potato stem borers and hopvine borers are occasional pests of field corn in New York, especially in weedy fields.
Symptoms of injury are dead whorls in corn plants from 2 to 12 inches in height and a borer hole at or below ground level. An active whitish larva with a brick red color on its upper side will be found at the base of the plant. These symptoms should not be confused with those of the common stalk borer, which attacks the corn plant a few inches above the ground level. The potato stem borer also attacks a variety of other crop plants and weeds. In cornfields it is particularly associated with quackgrass and curled dock.
A related insect, the hopvine borer, has been found infesting corn in several central New York counties. It is very similar to the potato stem borer in appearance, life cycle, and injury, but occurs about a month later.
Both species are relatively poor flyers and tend to be localized problems. Improved grassy weed control in cornfields is the best control recommendation known.