Monitoring for Common Stalk Borer Back »

Written collaboratively by Adam Varenhorst, Philip Rozeboom, Laura Edwards, Amanda Bachmann, and Patrick Wagner.


With hot temperatures occurring this past week, a lot of degree days have accumulated. However, common stalk borer activity likely remains limited to grass and weeds bordering fields. Although the common stalk borer is considered a minor pest, it can cause issues in the border rows of fields. Common stalk borers are an early season pest that initially feeds on corn leaves. As they grow, they move to the whorl of the plant and bore into the growing point. This activity can result in dead heart and subsequent plant death.

With hot temperatures occurring this past week, a lot of degree days have accumulated. However, common stalk borer activity likely remains limited to grass and weeds bordering fields. Although the common stalk borer is considered a minor pest, it can cause issues in the border rows of fields. Common stalk borers are an early season pest that initially feeds on corn leaves. As they grow, they move to the whorl of the plant and bore into the growing point. This activity can result in dead heart and subsequent plant death.

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. At this point corn should begin to be scouted. 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

Table 1. Color coded key for common stalk borer caterpillar activity based on accumulated degree days.
Accumulated Degree Days Common Stalk Borer Caterpillar Activity Recommendation
0-574 Conditions becoming favorable for egg hatch. Scouting is not necessary.
575-749 Eggs will begin to hatch. Scouting is not necessary.
750-1299 Young caterpillars will bore into stalks of 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 begin moving into adjacent corn. Continue scouting for defoliation.

 

Table 2. Common stalk borer activity based on degree day accumulation for South Dakota.
Location Accumulated
Degree Days Since
January 1, 2018
Recommendation
Buffalo 773 No scouting necessary.
Newell 711 No scouting necessary.
Rapid City 937.5 Avoid spraying weeds bordering field.
Hot Springs 1062.5 Avoid spraying weeds bordering field.
Lemmon 802 Avoid spraying weeds bordering field.
Faith 724 No scouting necessary.
Cottonwood 874.5 Avoid spraying weeds bordering field.
Mission 873.5 Avoid spraying weeds bordering field.
Selby 773 Avoid spraying weeds bordering field.
Gettysburg 761 Avoid spraying weeds bordering field.
Pierre 890 Avoid spraying weeds bordering field.
Winner 989 Avoid spraying weeds bordering field.
Aberdeen 849.5 Avoid spraying weeds bordering field.
Huron 899.5 Avoid spraying weeds bordering field.
Tyndall 956 Avoid spraying weeds bordering field.
Sisseton 845.5 Avoid spraying weeds bordering field.
Brookings 733 No scouting necessary.
Vermillion 1039 Avoid spraying weeds bordering field.
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