Written collaboratively by Adam Varenhorst, Philip Rozeboom, Patrick Wagner, and Brad McManus.
Originally Submitted: May 24, 2024
Parts of South Dakota are currently at, slightly below, or over the 1,080 degree days for the peak second generation emergence of seedcorn maggots (Figure 1). Much of the state is still approaching the peak emergence for the second generation. For areas that are beyond the 1,080 degree days, the next milestone will be 1,800 degree days for the peak emergence of the third generation. As a reminder, management of seedocorn maggots needs to occur prior to planting, and insecticide seed treatments are an option.
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 |
