Perennial ryegrass growing degree days (GDD)
Perennial ryegrass GDDs will be tracked during the 2025 growing season with comparisons to the previous seven years. The accumulation of GDDs will begin after the snow has melted from the perennial ryegrass fields and continue through swathing. A base temperature of 32 °F will be used for perennial ryegrass GDD model.
- Year-to-date GDD = 2,891 (Table 1)
- GDD last week (July 21 - 27) = 260 or 37.1/day; long-term average = 234 or 33.4/day
- GDD forecast for the next 10 days = 345 or 34.5/day
- Average GDD accumulation for the first week of August = 229 or 32.7/day
- The 10-day forecast suggests above average temperatures for the first week of August. Projected GDD is 34.5/day compared to the long-term average of 32.7/day
| Year | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2025 vs. 2024 |
|---|---|---|---|---|---|---|---|---|---|
| March | 0 | 0 | 0 | 0 | 131 | 30 | 0 | 0 | 0 |
| April | 229 | 296 | 93 | 95 | 236 | 183 | 211 | 184 | -67 |
| May | 812 | 653 | 959 | 649 | 640 | 600 | 548 | 815 | +159 |
| June | 932 | 859 | 1,064 | 959 | 1,007 | 995 | 919 | 1,007 | +73 |
| July | 918* | 1,119 | 985 | 1,104 | 1,174 | 1,179 | 1,067 | 1,100 | N/A |
| Total | N/A | 2,927 | 3,101 | 2,807 | 3,188 | 2,987 | 2,745 | 3,106 | N/A |
General crop condition
Perennial ryegrass swathing will continue with a few fields harvested this week.
Crop management
Spring wheat harvest is right around the corner. In the last few weeks, Canada thistle, downy bromegrass, foxtail barley, lambsquarters, pigweeds, wild oats, and other weeds are now visible over the top of the wheat canopy. From the combine seat, when harvesting wheat fields underseeded to ryegrass, would be a good time to make a mental note, or better yet make a weed map of these problem weeds. A weed map developed from the combine will help identify these problem weed areas in next year’s perennial ryegrass field.
Pest management
Isolated pockets of armyworm larvae have been reported in ryegrass fields. Monitor ryegrass fields as the heavy armyworm flights in late June and early July could have larger worms by the end of July.
This will be the last ryegrass newsletter for the season as ryegrass swathing should be in full swing this week.