Written collaboratively by Adam Varenhorst, Philip Rozeboom, Patrick Wagner, and Brad McManus.
Article Originally Submitted: May 17, 2024
Based on accumulated degree days, areas in southern South Dakota are approaching the peak emergence period for the second generation of seed corn maggots (Figure 1). As a reminder, seedcorn maggot management must be done before planting, or the populations can be avoided by not planting during times of peak emergence. With the forecasted rain for next week there may be an increased risk for seedcorn maggot infestations.
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 degrees Fahrenheit and an upper developmental threshold of 84 degrees Fahrenheit.
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
| Accumulated Degree Days |
|
|---|---|
| 360 | Overwintering generation |
| 1080 | Second generation |
| 1800 | Third generation |
