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Seedcorn Maggot Degree Day Activity Estimates: May 12, 2022

Originally Submitted: May 12, 2022

For most of South Dakota, we have accumulated enough degree days that the peak emergence of the overwintering population has passed. However, we are now approaching peak emergence of the second generation (Figure 1). Seedcorn maggot management must be done before planting, or the populations can be avoided by not planting during times of peak emergence.

Predicting Seedcorn Maggot Emergence Activity With Degree Days

The emergence of seedcorn maggot flies can be estimated by using degree days with a lower developmental threshold of 39°F and an upper developmental threshold of 84°F. The peak emergence for the overwintering population occurs at 360 degree days. The peak emergence for the second generation occurs at 1080 degree days. The peak emergence for the third generation occurs at 1800 degree days (Table 1).

As a reminder, the equation for degree days is:

(Maximum Daily Temperature + Minimum Daily Temperature) ÷ 2 - The Developmental Threshold

Map of South Dakota with locations indicating how many degree days have been accumulated. For assistance reading this graphic and data set, please call SDSU Extension at 605-688-4792.
Figure 1. Seedcorn maggot emergence activity based on degree day accumulation for various South Dakota locations as of May 12, 2022.

Table 1. Seedcorn maggot emergence activity
based on accumulated degree days.

Accumulated Degree Days
Seedcorn Maggot Peak Emergence
360 Overwintering generation
1080 Second generation
1800 Third generation

Related Topics

Corn Insects, Soybean Insects