Turfgrass Winterkill Prevention for Golf Courses

When turfgrass looks healthy and crisp in the fall and turns up dead in the spring, winterkill is the likely culprit. Simply put, winterkill is a catch-all term used to describe a loss of turf during the winter months. Winterkill doesn’t have a particular region it thrives in, damaging grass in cool-season, warm-season, and transition zone geographies, making it a threat to courses everywhere.

There are several key issues that can cause turf death in the winter (which are grouped into the winterkill category), from low temperatures to desiccation. We’ll take an in-depth look into the five main causes of turf winterkill and how to prevent them, plus offer some product suggestions at the end.

Number One: Crown Hydration

Crown hydration, a silent threat lurking beneath the frozen surface, particularly affects greens and short-cut turf during late winter and early spring. As turf breaks dormancy, semi-frozen soils prevent water from percolating to drains, saturating the surface. A sudden drop to approximately 20°F after soil thaw can lead to flash freezing and rupturing of crown cells, resulting in death. Poa annua is particularly vulnerable, often the sole victim in a mixed putting green with creeping bentgrass.

Preventative Measures Against Crown Hydration

• Treat turfgrass in late fall with fertilizers low in nitrogen and high in potassium to bolster the plant’s energy reserves.
• Implement solid tine aeration to eliminate excess surface moisture.
• Rectify low areas prone to water accumulation on greens through surface contouring.
• Include a low-rate penetrant, such as Hydro-Pak Diversion, in the last spray application to reduce surface tension.

Number Two: Winter Desiccation

Winter desiccation happens when turfgrass lacks the protective insulation of snow cover during winter. Exposed to cold, dry winds, and low temperatures, the turf essentially gets freeze-dried—and if you’ve ever eaten astronaut food, you know it’s not going back to normal. This phenomenon poses a significant threat to creeping bentgrass, Poa annua, and bermudagrass, with elevated areas being particularly susceptible.

Preventative Measures Against Winter Desiccation

• Ensure adequate turf fertility with high potassium ratios before dormancy to build up energy.
• Use covers when applicable to shield turf from cold temperatures and wind. Note that this method is very hands-on and requires monitoring to ensure the covers stay put.
• Apply wetting agents like Hydro-Pak BioWet, Hydro-Pak Command, and/or Hydro-Pak Aqueous before turning off irrigation systems to help ensure adequate moisture and prevent desiccation.

Number Three: Ice Sheets

In the northern US, where winters can get particularly dicey (and icy), sheets of ice are a significant threat to turfgrass. Just like exposure to carbon monoxide can be fatal in a home, prolonged periods of ice accumulation can lead to fatal levels of carbon dioxide in turfgrass, since it restricts its ability to breathe. It’s important to note that creeping bentgrass and Poa annua both exhibit varying tolerance periods to ice accumulation.

Preventative Measures Against Ice Sheets

• Utilize solid tine aeration to release gas accumulations beneath the ice.
• Incorporate penetrants in the fall to facilitate water movement through the soil, preventing surface accumulation.
• Strategize penetrant use on courses in the transition zone, adding it to fall large patch or spring dead spot applications.

Number Four: Snow Mold

Snow mold, a fungal disease, can easily make surfaces unplayable. Northern regions like Wisconsin and Michigan are more prone to gray snow mold, while the transition zone and warmer areas face the less severe pink snow mold. Preventative applications can keep snow mold away, typically with one application (sometimes two).

Preventative Snow Mold Spray Best Practices

• Generally, it’s best to use products with more than one active ingredient, including multi-active products such as Enclave or Premion. In the northern US, some choose to have four different active ingredients in their fairway spray.
• For fall applications, putting Proxy in a snow mold spray will help suppress Poa annua seed heads, and adding PGR 113 can reduce growth and extend a fungicide’s effectiveness.

Number Five: Direct Low Temperature

Often uncited, but important to discuss, warm-season grasses—specifically perennial and annual ryegrass—are prone to direct low-temperature damage. This damage is accelerated during rapid temperature declines, as the turf simply cannot handle the shift. 

A heavy topdressing in the fall and/or applying covers gives superintendents the best chance of protecting susceptible turfgrass types from direct low-temperature damage. Plus, topdressing will also help combat crown hydration, ice sheets, and winter desiccation.

Temperature Guidelines for Winterkill

Understanding critical temperature thresholds for root and shoot growth is essential for proactive winter care and anticipating (as well as preventing) potential winterkill. Be sure to enact preventative measures before temperatures reach dangerous levels.

Warm-Season Turf

– 50°F: Root growth slows. Chilling injury possible.

– 25°F: Winterkill becomes possible.

– 17°F: Expect some degree of winterkill.

Cool-Season Turf

– 40°F: Shoot growth ceases.

– 33°F: Root growth ceases.

– 20°F: Low-temperature kill possible if temperature drops rapidly below 20°F.

Winterkill Prevention and Recovery Tips for Late Fall and Spring

There are a few things you can do and a few products you can apply to keep winterkill at bay.

While winterkill is dangerous to turfgrass, enacting proactive measures can make all the difference and ensure healthy tees and greens in the spring. Everyone’s course is different, so your specific needs may vary based on geography, types of turfgrass on your course, and more. To learn more about what products and solutions may be best for your course, reach out to your local ATS representative.