Originally Submitted: May 6, 2021
Temperatures are warming up, and we are beginning to accumulate degree days a little faster for common stalk borers. However, common stalk borer activity remains unlikely throughout South Dakota. Eggs will be hatching through much of the state, but the caterpillars will stay on weedy grass hosts for now. We will continue to monitor common stalk borer activity as the season progresses.
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. Corn should begin to be scouted at this point. 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
| Accumulated Degree Days |
Common Stalk Borer Caterpillar Activity |
Recommendation |
|---|---|---|
| 0-574 | Conditions favorable for egg hatch. | No scouting necessary. |
| 575-749 | Eggs begin to hatch. | No scouting necessary. |
| 750-1299 | Young caterpillars begin boring into grass and weeds. | No scouting necessary. Avoid spraying grass and weeds along field edges. |
| 1300-1399 | 10% of caterpillars begin moving into adjacent corn. | Begin scouting field edges for defoliation. |
| 1400-1700 | 50% of caterpillars moving into adjacent corn. | Continue scouting for defoliation along field edges. Spray if necessary. |
| Location |
Since January 1, 2019 |
Recommendation |
|---|---|---|
| Buffalo |
|
No scouting necessary |
| Newell |
|
No scouting necessary |
| Rapid City |
|
No scouting necessary |
| Hot Springs |
|
No scouting necessary |
| Lemmon |
|
No scouting necessary |
| Faith |
|
No scouting necessary |
| Cottonwood |
|
No scouting necessary |
| Mission |
|
No scouting necessary |
| Selby |
|
No scouting necessary |
| Gettysburg |
|
No scouting necessary |
| Pierre |
|
No scouting necessary |
| Winner |
|
No scouting necessary |
| Aberdeen |
|
No scouting necessary |
| Huron |
|
No scouting necessary |
| Mitchell |
|
No scouting necessary |
| Tyndall |
|
No scouting necessary |
| Sisseton |
|
No scouting necessary |
| Brookings |
|
No scouting necessary |
| Vermillion |
|
No scouting necessary |
