Written with contributions by Shelby Pritchard, former SDSU Extension Pest Management Specialist.
Originally Submitted: April 28, 2022
With corn planting underway in some parts of South Dakota, it’s time to start evaluating degree days for common stalk borer caterpillars. As temperatures eventually warm up, this pest can become a problem, especially around the borders of fields. Currently, no scouting is necessary for common stalk borer caterpillars in South Dakota (Table 1).
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°F. 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 1300 degree days, 10% of the caterpillars will begin moving to corn. Corn should begin to be scouted at this point. At 1400 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
| Location |
Since January 1, 2022 |
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 |
| 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. |
