Originally Submitted: June 3, 2021
Throughout South Dakota, we still haven’t reached the degree day accumulation levels to see common stalk borers moving into corn fields. However, if weeds and grass are sprayed out along field borders, there is a very high probability that common stalk borers will be forced into corn early.
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, 2021 |
Recommendation |
|---|---|---|
| Buffalo |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Newell |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Rapid City |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Hot Springs |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Lemmon |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Faith |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Cottonwood |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Mission |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Selby |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Gettysburg |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Pierre |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Winner |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Aberdeen |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Huron |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Mitchell |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Tyndall |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Sisseton |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Brookings |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
| Vermillion |
|
No scouting necessary. Avoid spraying grass and weeds along field edges. |
