Common Stalk Borer Activity Estimate: April 29, 2021

Originally Submitted: April 29, 2021

Temperatures are continuing to warm up, and we are beginning to accumulate degree days a little faster for common stalk borers. However, common stalk borer activity is still unlikely throughout South Dakota.

Predicting Common Stalk Borer Migration Into Corn Fields With Degree Days

The hatching and movement of common stalk borer caterpillars can be estimated by using degree days with a developmental threshold of 41 degrees Fahrenheit. Common stalk borer eggs typically begin to hatch at 575 degree days. The caterpillars finish hatching and begin development on weeds and grasses at 750 degree days. At 1,300 degree days, 10% of the caterpillars will begin moving to corn. At this point, corn should begin to be scouted. At 1,400 degree days, 50% of the caterpillars will or have moved into corn.

As a reminder, the equation for degree days is:

(Maximum Daily Temperature + Minimum Daily Temperature) ÷ 2 - The Developmental Threshold

In South Dakota, most of the state is still between conditions approaching egg hatch and egg hatch occurring. No scouting is necessary for common stalk borer at this time. We will continue to update this information.