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What you need to know about pink snow mold

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Pink snow mold, characterized by the color of its patch edges, targets both blade and root in affected grass. (Photo: Nufarm)
Pink snow mold, characterized by the color of its patch edges, targets both blade and root in affected grass. (Photo: Nufarm)

Lawn care operators (LCOs) in prone areas need to take steps to prevent pink snow mold. Here’s what the experts told us.

Environmental factors

Aaron Hathaway
Aaron Hathaway

Pink snow mold (Microdochium patch) is one of the diseases LCOs will notice first in the spring, though it can occur anytime temperatures are 30 to 60 degrees Fahrenheit, says Aaron Hathaway, technical services manager for turf and ornamentals, Nufarm.

“It can easily be confused with gray snow mold at this point, but if there was never any snow cover, turf managers can be sure it isn’t gray snow mold, as pink snow mold doesn’t need snow cover to develop,” Hathaway says.

Pink snow mold rarely causes more than aesthetic issues; turfgrass usually recovers as temperatures and sunlight increase. However, it can be a destructive disease in areas like the Pacific Northwest in the winter when there are few other pathogens to compete with, Hathaway says.

Pink snow mold typically attacks bluegrasses, fescues and ryegrasses. Bentgrasses are the most susceptible type of turfgrass.

In extreme situations, LCOs can apply fungicides before snowfall — though turf dormancy is often enough to knock down the pathogen, Hathaway says. Even if there are foliar symptoms after winter, that doesn’t mean the turf is dead.

“Once growth resumes, moderate levels of nitrogen can help to push growth and recovery,” Hathaway says.

Cultural practices

Ben Pease
Ben Pease

Symptoms of pink snow mold include circular to irregularly shaped patches of pink or salmon-colored fungal growth on the lawn, says Ben Pease, Ph.D., turfgrass agronomist for The Andersons plant nutrient group. The patch areas can range from a few inches to several feet in diameter and may have a slimy or matted appearance.

Cultural practices to prevent snow mold include mowing at the optimal height for the turf species, avoiding excessive nitrogen applications in the fall, using a slow-release fertilizer during the growing season, irrigating in the morning, using thatch-reduction products like humic acid and performing core aeration on a yearly or twice-yearly basis, Pease says.

If there’s damage from pink snow mold, operators should gently rake the matted areas to encourage air movement. “Overseed the affected area with disease-resistant turfgrass cultivars,” Pease says. “Apply slow-release granular fertility to help encourage regrowth of unaffected areas or seedlings.”

Snow mold differences

Matt Giese, Field technical manager, Syngenta
Matt Giese

The best way to reduce or prevent damage from pink snow mold is to plan for fungicide applications in the fall after mowing has ceased but before there’s permanent snowfall, says Matt Giese, technical field manager, Syngenta. Snow mold can be a challenge to manage because visible symptoms are generally not observed until spring melting begins.

“Fortunately, fungicide treatments are effective at suppressing pink snow mold in the spring after the snow has melted, which is not the case with gray snow mold, and damaged areas can persist well into the summer months before full recovery occurs,” Giese says.

Granular and liquid fungicide applications are also best applied in a preventive manner.

“Granular is sometimes best because it does not require a separate tank to be mixed and can be spot-treated to areas of known infestation and only on certain customers’ lawns,” Pease says. “Fungicides containing thiophanate-methyl or azoxystrobin plus propiconazole are excellent options. Chlorothalonil can also be used.”

Pink and gray snow molds can also occur concurrently in a lawn. While separated by the color in their names, that’s not always a good way to differentiate between them, Giese says.

“Close inspection of the turfgrass leaves infected by pink snow mold will indicate the absence of sclerotia-like structures that are only present with gray snow mold infestations,” he says.

To prevent pink snow mold, operators should avoid heavy applications of water-soluble nitrogen sources in the late fall prior to dormancy.

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