Snow mould is one of the most prominent turfgrass diseases in Canada1. Commonly found in areas with heavy snowfall, the disease creates rings of discolouration as the roots, stems and leaves of infected grasses rot2. Though there are many types of snow moulds, gray snow mould (a.k.a. Typhula blight or snow scald) and pink snow mould (a.k.a. Fusarium patch) are the most commonly seen types throughout the country1.
Both grey and pink snow moulds are caused by cold-tolerant fungi that grow in high levels of moisture at freezing or near-freezing temperatures, typically between -3º to 15º C2. While pink snow mould can begin to develop in cool, moist conditions prior to snowfall2, grey snow mould most commonly develops under snow cover from winter to late spring and is most severe where snow accumulates in large banks or drifts, or where snow falls on unfrozen turf, as both of these instances create excess moisture that allows fungal bodies to thrive3.
How to identify grey snow mould
This type of snow mould is most active in early spring, when turf begins to thaw and snow melt produces high levels of moisture. During this time of year, grey snow mould first appears as a roughly circular, white or grayish white area with regular margins. Over time, infected areas can combine to form irregular, straw-coloured patches up to 2 or 3 feet in diameter2.
The wet grass may become matted and covered with fluffy, grayish white mycelium speckled with pale- to dark brown sclerotia. Sometimes, the mould may turn bluish gray to almost black, while other times, a silvery, membranous crust develops over the infected grass2. However, the presence of sclerotia is the best indicator of grey snow mould1. These structures are most commonly found immediately after snow melt — later in the spring, they dry up and are no longer visible1.
How to identify pink snow mould
Typically, pink snow mould first appears as round, water-soaked spots between one and three inches in diameter. As the disease progresses, patches take on a yellow, orange brown or reddish-brown hue, and mould growth can be either sparse or abundant. As they enlarge, infected spots become ring-like and light gray or tan in colour, with an orange brown or brown border. Though rounder and smaller than its grey cousin, pink snow mould can grow up to 8 to 12 inches in diameter and can even merge to cover large areas2.
Patches of the disease may persist until snow cover develops, and they can increase in size until snow melt. At this time, the fungus is exposed to light, which lends it its characteristic pink hue2.
Control tips
For best results, use a combination of cultural and chemical methods in the fall to help prevent snow mould damage. To keep turf from matting, mow regularly3, especially in the weeks leading up to the first major snowfall of the year. Additionally, avoid applying nitrogen fertilizers within six weeks of expected snowfall, as they help provide succulent tissues for the fungus to feed on1.
Most snow mould fungicides registered in Canada are effective against both pink and grey types1, though it’s important to check the label beforehand. A single application in the fall prior to the first permanent snow of the season is typically sufficient. However, the use rate that’s right for your fairway depends on the condition of your turf before snowfall and whether it has a history of snow mould: choose the lower rate as a preventative measure; choose the higher rate for curative purposes2.
After snowfall, use snow fencing, windbreak plantings or other methods to help prevent snow drifts from forming1. In the spring, areas with heavy snow accumulation take longer to melt, creating excess moisture for a prolonged period — the perfect breeding ground for snow mould to spread. In the spring, if snow cover is so deep that it could take several weeks to fully melt, you may want to consider using fertilizer or topdressing to hasten the melting process1. Once the snow is fully melted, speed up drying by raking matted grass, and help encourage growth of healthy turf by fertilizing damaged areas3.
Though snow mould can cause inconvenient, costly damage to golf course greens, tees and fairways, a few extra steps in the fall can help minimize damage in the spring. INTAGLIO™, our snow mould fungicide, is formulated especially for Canadian conditions, with effective, long-lasting control and three of the most potent active ingredients. Click here to see if INTAGLIO is right for your turf.
References and Additional Reading
1Hsiang, Tom. “Controlling Grey Snow Mould and Take-all Patch Diseases.” Western Canada Turfgrass Association. January 2000. Online. https://bit.ly/2NlxxW9
2“Snow Moulds of Turfgrasses.” Integrated Pest Management, University of Illinois Extension. July 1997. Online. https://bit.ly/2M6XAvz
3“Gray Snow Mould.” PennState College of Agricultural Sciences, Center for Turfgrass Science. Online. https://bit.ly/2NjQ19D