Stalk borer eggs have hatched and many larvae are now in brome or other grasses bordering corn. Some stalk borers already may be in corn because they hatched from eggs that were laid on grass or giant ragweed out in the field last fall, or they moved directly into border row corn instead of the grass when they hatched. Most stalk borers that hatch in grass stay there until they grow to a size that is too big for the grass stem. Then they migrate in search of larger diameter plants, which often is corn. This article discusses management for stalk borers only in grass adjacent to corn.
Top number shows degree days.
Bottom number shows expected date for 10 percent migration. The predicted dates for the early stages of stalk borer migration are shown in the map. These dates predict when about 10 percent of the larvae will move out of brome grass. When 1,300-1,400 degree days have occurred in your area, scout to determine if the larvae are moving into corn. Begin by scouting corn adjacent to grass terraces, waterways, fence lines, or where stalk borer damage occurred last year.