Pink snow mold, spotted in the image above, is one of several winter turf diseases to monitor when your crews hit the field again this spring.
Photo courtesy of Paul Koch

Turfgrass experts say most winter turfgrass diseases won’t be catastrophic this year – particularly the various type of snow mold that spring up when 2021 rolls around.

And while proper prevention methods are the best ways to tackle turfgrass diseases, there are some ways to keep lawns healthy even after temperatures rise again.

“By the time we get to January, there’s not a lot we’re doing to prevent those diseases, so now we’re at the point where we’re trying to recover as quickly as we can,” says Paul Koch, an associate professor at the University of Wisconsin – Madison.

Koch says the winter diseases can really be defined by whether or not there’s snow cover in that particular region of the country. Where there is snow, the snow molds – speckled, gray and pink – are all more likely to pop up. In areas of the country where there isn’t much snow, contractors could deal with more leafspot or large patch diseases.

“If we get snow down here, it’s generally here today and gone tomorrow,” says Clint Waltz, an extension specialist at University of Georgia Extension. “It’s more wet conditions than anything else, and then compound that with possible drying conditions, that generally doesn’t facilitate disease when it gets dry.”

“It always helps to know what you’re dealing with...You want to make sure that you have an accurate diagnosis.” Paul Koch, associate professor with the University of Wisconsin-Madison

Identifying the diseases.

By the time landscapers start encouraging turf growth in the spring, Koch says plants usually are recovering from their dormant periods.

The issue with finding the right treatment is that many of the diseases look similar at first glance, particularly snow molds. They all produce circular patches about one to three feet in diameter, though pink snow mold contains a reddish ring around the outside while gray snow mold produces structures called sclerotia, which survive in dead leaf tissue. These look like red pebbles or sand granules. Meanwhile, speckled snow mold simply looks like somebody sprinkled pepper on the turf.

Other cool-season turf diseases found up north or in colder parts of the western United States are Pythium blight, which produces slick, brownish blotches in the turf, and powdery mildew, a more serious issue that leaves the turf looking like it’s been sprayed with white dust.

Koch says leaf spot can affect both cool- and warm-season turf, though it seems to be a little more common in areas that don’t experience much snowfall. These can be identified by finding spots on leaves as the name implies.

Diseases like large patch, meanwhile, are also a little easier to decide because the issue is obviously spread right across the turf. These are often found on St. Augustine, zoysiagrass, centipede and Bermudagrass turfs. Dollar spot and brown patch are also issues for these types of turf.

But Koch also says talking with an extension specialist, particularly locally, can help contractors best navigate these winter diseases. It’s easy to get one disease confused for another, and treatments can vary. He recommends treating and monitoring the infected areas for about a month before then reaching out for help to see if someone knows what to do.

“It always helps to know what you’re dealing with,” Koch says. “You may think the issue that you had was snow mold, but it may be something else. You want to make sure that you have an accurate diagnosis.”

Gray snow mold, found here on a bluegrass lawn, is often mixed up with pink or speckled snow molds.
Photo courtesy of Paul Koch

A year-round affair.

In areas with warmer climates, turf disease is an ongoing fight, though wintertime actually provides some much-needed reprieve.

Waltz says most warm-season grasses are more susceptible to diseases during transition seasons like fall and winter. There are some exceptions, he notes, but generally, this time of year actually slows down diseases for folks down south. In fact, if contractors are just noticing winter turfgrass diseases during the winter months, chances are strong that they’re seeing the remnants of a fall disease, Waltz says.

“It’s not going to get better over the wintertime,” Waltz says. “If you had patch over October, that spot didn’t disappear in December or January. Because it was there in the fall, it still will be there in the spring.

The issue is knowing when to apply product – it’s easier to go too early in places where it’s relatively warm all the time. Waltz recommends waiting until temperatures are a little more consistent. To be specific, he says soil temperatures four inches deep in the ground should be about 65 degrees or higher.

Fertilizing too soon will only invite turfgrass diseases to come in during the spring, Waltz says.

“Disease doesn’t go to zero, but it certainly slows down this time of year for us,” he says.

Ways to constantly combat turfgrass diseases include raking off leaves and debris from the turf constantly. Allowing the turf to retain all the moisture from beneath the leaves over an extended period of time is often what causes the diseases in the first place.

“I think getting that off can help mitigate disease as much as anything,” Waltz says. Regarding raking, Koch adds that it increases the temperature of the grass, fending off any further damage from the disease.

“It’s going to have sunlight penetrate deeper into the canopy and increase oxygen flow in the area,” Koch says.

There's always next year.

As far as turfgrass diseases go, Koch says the best way to avoid them is simply taking preventative measures. Applying nitrogen products, for instance, should stop by the end of September or end of October.

“When we get later in the fall, you’re stimulating growth when it really should be slowing down,” Koch says, adding that the plants are trying to shut themselves down to protect themselves during the winter.

Improving drainage around the turf also helps prevent diseases, as water or other moisture that pools up together in one spot is often a culprit for turf issues. Plus, Koch says once a diseased spot is found, landscapers should avoid walking through it, spreading the disease from one spot to another.

And, of course, mowing at an appropriate height during the season also helps keep the turf healthy. This helps keep conditions bad for fungal growths and good for proper turf growth at the same time. For most types of grasses, keeping lawns at a three-inch height is about right, though this is just the recommended mowing height. It could vary based on the situation or even the type of turf.

“(Treatment is) a matter of changing the environment again to make it less suitable for disease to grow,” Koch says. “If things aren’t healing, you need to reach out to an expert. It’s a case-by-case basis with an extension specialist.”