Common Stalk Borer Activity Estimate: May 13, 2021

Originally Submitted: May 13, 2021

The upcoming weather forecast looks warmer than the last few weeks, and that means we will begin to accumulate degree days for insect pests, like the common stalk borer, at an increased rate. At this point in time, common stalk borer activity is still going to be limited to broadleaf and grassy weeds. We are reaching a point where weed management around field borders should not be continued, as the common stalk borers will soon be outgrowing those hosts and beginning their search for larger hosts nearby.

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