Written collaboratively by Adam Varenhorst, Philip Rozeboom, Patrick Wagner, and Brad McManus.
Originally Submitted: June 6, 2024
Peak emergence of the second generation of seedcorn maggots is occurring in a few areas of the state. The rest of the state is between the second and third generation emergences, with areas in southern South Dakota likely reaching peak emergence of the third generation sometime next week.
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 |
