Common Winter Turfgrass Diseases
Winter can be a tough season for turf, and as temperatures drop and snow begins to fall, certain diseases can take hold, leaving your beautiful turfgrass damaged.
Among the most common culprits affecting turf in winter are Gray Snow Mold and Pink Snow Mold. Recognizing the symptoms and understanding the steps to manage and prevent these diseases can make all the difference in protecting your lawn as winter ends and spring begins. Below, we’ll walk you through everything you need to know about these winter turfgrass diseases, from identifying symptoms to implementing cultural and chemical control measures to keep your turf healthy.
Symptoms
Gray Snow Mold
Gray snow mold is caused by two species of Typhula fungi (T. incarnata and T. ishikariensis) and thrives under prolonged snow cover. Symptoms usually surface once the snow begins to melt, revealing circular or irregular patches of damaged turf up to 3 feet or more in diameter. These patches appear grayish-white, with matted-down turf, often showing tan or brown sclerotia (small, pea-like fungal structures) on the infected leaves. Left unmanaged, gray snow mold can kill large areas of turf, often leading to slow recovery come spring.
Pink Snow Mold
Pink snow mold, caused by Microdochium nivale, develops under cold and often snowy conditions. Symptoms include circular patches ranging from 2 inches to 1 foot in diameter that are white or light tan. A distinctive salmon-pink ring often forms along the edges of these patches when the disease is actively growing. Leaves within the affected areas tend to collapse and mat down. While pink snow mold thrives under snow, it can also develop during cool, wet weather without snow cover.
Development Factors
Gray Snow Mold
Gray snow mold requires extended snow cover (typically 60 days or more) to develop. It’s particularly severe when snow falls on unfrozen ground. The fungal pathogens survive summer as sclerotia in the soil or thatch, germinating when fall temperatures are between 50°F and 65°F. Dense, lush turf growth caused by excessive nitrogen fertilization, high mowing heights, or infrequent mowing increases vulnerability. Additionally, accumulations of snow, leaves, or mulch on turf create ideal conditions for disease development.
Pink Snow Mold
Pink snow mold thrives in cold conditions, especially when snow falls on unfrozen ground. However, it doesn’t always need snow to develop; cool, wet weather (below 60°F) is also conducive. Contributing factors include excessive thatch buildup, restricted air movement, and poor soil drainage. Heavy traffic and inadequate soil potassium levels can also increase the risk. Pink snow mold may develop under tree leaves that remain on turf for long periods during cold, wet conditions.
Cultural Control
Taking a proactive, cultural approach to turf management is critical in reducing the risk of both gray and pink snow mold. Here’s how you can minimize their impact and maintain a healthy lawn through winter.
- Mowing: Continue mowing your turf until foliar growth stops completely in late fall. Avoid letting the grass grow too tall heading into the winter season, as dense, lush foliage is more prone to snow mold infections.
- Avoid Excess Nitrogen: Refrain from applying nitrogen fertilizers before anticipated cold weather or prolonged snow cover, as these can create ideal conditions for disease development.
- Leaf and Debris Removal: Frequently remove leaves and debris from your turf during autumn and winter to prevent them from trapping moisture and promoting fungal growth.
- Snow Management: Minimize the duration of snow cover in areas prone to mold. Erect snow fences or strategically plant landscape vegetation to prevent heavy accumulation. Avoid compacting snow on your turf by limiting foot or equipment traffic, as compacted snow melts more slowly and encourages disease.
- Aeration and Drainage: Improve surface drainage, aerify compacted areas, and reduce thatch buildup to prevent waterlogging and improve airflow. Prune trees to enhance air movement and reduce shade.
By adopting these cultural practices, you’ll help create an environment that is less hospitable to snow mold pathogens.
Chemical Control
For persistent snow mold problems, preventative fungicide applications can be highly effective.
Gray Snow Mold
- Timing: Apply fungicides in late fall, preferably after your last mow but before the first snowfall.
- Best Practices: Use tank mixtures that combine different fungicide chemistries for optimal results. Always follow label instructions and consult local extension services for the latest recommendations.
Pink Snow Mold
- Timing: Preventative fungicide applications should also be made in late fall before snow cover. For regions without consistent snow cover, fungicides can be applied when symptoms first appear.
- Spot Treatments: If pink snow mold is an issue in localized areas, focus your chemical applications there to reduce costs and environmental impact.
Preventative fungicides are invaluable when combined with cultural controls, especially in areas with a history of severe snow mold outbreaks. They can significantly limit the disease and ensure your turf recovers quickly once winter is over.
Keep Your Turf Snow Mold-Free This Winter
Winter turfgrass diseases like gray and pink snow mold can be challenging, but with diligent attention to cultural practices and preventative treatments, you can protect your turf from significant damage. By preparing in fall and staying proactive during winter, you’ll enjoy a healthier, greener turfgrass come springtime.
Here’s to a snow mold-free winter and vibrant spring!
