Seed Production Newsletter - June 24, 2025

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 = 1,711 (Table 1)
• GDD last week (June 16-22) = 254 or 36.3/day; long-term average = 212 or 30.3/day
• GDD forecast for the next 10 days = 355 or 35.5/day
• Average GDD accumulation for the end of June = 220 or 31.4/day
• The 10-day forecast suggests above average temperatures for end of June. Projected GDD is 35.5/day compared to the long-term average of 31.4/day

General crop condition

Many perennial ryegrass fields are in the heading  and in varying stages of pollen shed. The recent rains and thunderstorms can result in lodging of perennial ryegrass that exhibits lush growth. With dry weather lodged ryegrass tends to become more erect in a few days, especially if previously treated with a growth regulator.

Summer grass seed tour

The annual grass seed summer tour is scheduled for June 26 with the field tour to begin at 5:00 p.m. at the U of MN Magnusson Research Farm. 

Directions to the U of MN Magnusson Research Farm: At the intersection of MN Hwy 11 and 310, proceed north on MN 310 for two miles, turn left (west) on Roseau County 16, and proceed west for approximately three miles. The U of MN Research Farm is located on the north side of Roseau County 16. 

Dr. Nancy Ehlke, U of MN grass seed breeder, will provide an update on the U of MN ryegrass breeding program. Dr. Eric Watkins will highlight research with hard fescues. Donn Vellekson will lead a tour of the perennial ryegrass field trials to include: preemergence herbicides, fertility, postemergence herbicides, growth regulators and a perennial ryegrass variety trial. 

Crop management

The USDA-ARS tracks rust development and movement from the Gulf of Mexico to the northern plain states. Rust movement on air currents from southern states has been called the Puccinia Pathway.

Historically, in northern MN environmental conditions, crown rust has been observed after 1,500 and leaf and stem rust after 1,900 GDD. Rust spores travel on low level jet stream winds from southern states into the perennial ryegrass production areas of northern MN. Perennial ryegrass is heading, and many fields are in full head extension. To maximize perennial ryegrass seed yield, it is important to protect the entire ryegrass seedhead from diseases that can reduce the photosynthetic area of the seedhead. The following are strategies for rust control in perennial ryegrass post heading. 

1. Scout ryegrass fields for rust a couple times a week as in favorable environmental conditions rust can develop and increase rapidly and this disease can “explode” in a few days.
2. If a fungicide has been applied with a previous trip across the field, apply a fungicide when the last fungicide is about to “run out.” The number of days for disease protection will depend upon the fungicide used and product rate.
3. Fungicide applications when the ryegrass seedhead is fully extended will provide protection of the entire seedhead. A full rate of Priaxor or Quilt Excel at full head extension should provide protection for 21 to 28 days. As of June 22, the year-to-date accumulated GDD was 1,711. The new 10-day forecast is for 35.5/day and if that forecast holds true the July 1 GDD will be 2,066 which will be in the historical window for leaf and stem rust infection in perennial ryegrass seed production.

Pest management

Armyworm moth capture continue to be low in 2025. Last week’s moth numbers ranged from 0 to 6 with a seven trap average of 3.1/trap.

Low levels of grasshoppers have been observed in perennial ryegrass fields. Weather conditions and crop scouting will determine if control measures are warranted.

Next week’s newsletter will be released on July 1.