Also, spring-applied herbicides normally do not kill the grasses quickly enough to prevent borer survival. Weeds killed this summer will make the field less attractive for egg laying this fall and reduce PSB damage next year. Insecticide control of potato stem borer is impractical because in most instances the larva will have done most of its damage before its presence is spotted. Determining infestation levels by survey before plant injury occurs is practically impossible. The larvae are very small, making them very difficult to find.
Spotty infestations necessitate sampling many areas of the field.
Often only the outer rows of corn in a field are infested, especially if the corn borders on grassy areas with suitable weed hosts. If larval detection was possible before the appearance of plant injury, an effective granular insecticide would have to be applied post-emergently over the seedling row because the larvae migrate from plant to plant over the soil surface. Edited in April 1997, based on material developed in 1985. Lawrence K. Forcier, Director, University of Vermont Extension, Burlington, Vermont. University of Vermont Extension and U.S. Department of Agriculture, cooperating, offer education and employment to everyone without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.