Written collaboratively by Adam Varenhorst, Brad McManus, Philip Rozeboom, and Patrick Wagner.
Originally Submitted: May 9, 2024
With the cool, wet start to the 2024 season, it is important to consider the possibility that seedcorn maggots could cause issues for crop seedlings. In South Dakota, enough degree days have accumulated for the overwintering generation of seedcorn maggots to be active. We are now approaching the peak emergence for the second generation of seedcorn 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.
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 |
