By Adam Varenhorst
There weren’t a lot of degree days accumulated during the last week. Many areas have reached peak emergence for the second generation of seed corn maggots, while others are still approaching it (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
Figure 1. Seedcorn maggot emergence activity based on degree day accumulation for various South Dakota locations as of May 26, 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 |
Source : sdstate.edu