Common Stalk Borer Activity Estimate: May 27, 2021

Originally Submitted: May 27, 2021

Throughout South Dakota, we still haven’t accumulated enough degree days for common stalk borers to begin moving into corn, which is a good thing. At this point in time, common stalk borer activity is still going to be limited to weeds and grassy weeds. With the cooler temperatures in the forecast, there won’t be a lot of degree days accumulating over the weekend.

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

Table 1. Common stalk borer caterpillar activity
based on accumulated degree days.
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.

Table 2. Common stalk borer activity based on
degree day accumulation for South Dakota.
Location
Accumulated Degree Days
Since January 1, 2019
 Recommendation
Buffalo
915
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Newell
814
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Rapid City
899
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Hot Springs
994
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Lemmon
947
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Faith
882
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Cottonwood
913
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Mission
985
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Selby
880
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Gettysburg
801
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Pierre
1002
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Winner
1125
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Aberdeen
989
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Huron
1006
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Mitchell
1099
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Tyndall
990
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Sisseton
935
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Brookings
746
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.
Vermillion
1177
 No scouting necessary.
Avoid spraying grass and
weeds along field edges.

Related Topics

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