Regardless of the turf species, there are general best practices for healthy lawns, says Zac Reicher, Bayer Green Solutions Team. “Shade, compaction, poor drainage and traffic are common factors contributing to poor health and thus lawn diseases,” he says. “Reducing the severity of some or all of these will maximize turf health and minimize disease regardless of species.”
To combat these diseases, Matt Giese, technical services manager for Syngenta, recommends avoiding too much or too little fertilization and irrigation, which can weaken stands of turf. “Overwatering invites water-loving diseases to gain a foothold in turfgrass systems, so moderation is key,” he says. But if rainfall is high, fungicide applications become necessary.
Reicher says turfgrass prefers dry soils to wet soils and most irrigated lawns are over-watered, so water only as needed to limit drought stress, which might require daily or weekly adjustments. “Most irrigated lawns are over-irrigated,” he says. “It’s always better agronomically to err on the dry side rather than the wet side,” he says. “Plus, you will save water.”
Going into and coming out of winter, spring dead spot, which is caused by a soil-borne pathogen, is common on warm season grasses.
Photo courtesy of PBI Gordon
Cool season grasses.
Diseases generally take hold of cool season grasses when snow falls on grass that’s just above freezing, says Brian Aynardi, PBI Gordon manager of university and contract research for the northeastern U.S.
Prolonged snow coverage leaves grasses susceptible to gray snow mold, which pops up when snow cover lasts for 45 days or more, allowing the typhula pathogen to germinate.
“Underneath snow cover, it starts to infect those leaves and it starts to cause patches to develop,” Aynardi says. “So you don’t actually see any of this going on. Under snow cover is where infection and patch development occurs.”
When the snow melts, you’ll start to see patches that can range from several inches to several feet in diameter. To differentiate gray snow mold, also known as speckled snow mold, look for specks on leaves about the size of a pinhead. They’ll vary in color from pinkish to almost black.
Those specks are called sclerotia – hardened mycelia that absorb nutrients and can survive over the summer. They’ll fall on the ground or lay underneath green tissue, leading to breakouts the following year.
“It’s always better agronomically to err on the dry side rather than the wet side.” Zac Reicher, Bayer Green Solutions Team
There is a limited number of fungicides on the market available for lawn care, but flutolanil, azoxystrobin and fluoxastrobin are effective active ingredients, manufacturers say.
Typically, they’ll be mixed with chlorothalonil, Aynardi says. “Chlorothalonil is labeled for home lawn use and anything you’re going to spray is portably going to be better served with some chlorothalonil.”
Another common winter disease, pink snow mold, expands further into the growing season. Caused by Microdochium nivale, it will grow both under snow cover and without it, ranging in temperatures from just above freezing to about 60 degrees.
To find it, look for patches anywhere from 2 to 6 inches in diameter. Under sunny conditions, it will look pink around the edges. It looks similar to gray snow mold since both create a cream-colored tissue when the grass is destroyed.
If you’re unsure which disease is affecting a lawn, look for the distinguishing sclerotia to see if it’s gray snow mold. If you don’t see any, look under a microscope for the lunar-shaped specks that accompany pink snow mold.
Strobilurin fungicides, polyoxin D, chlorothalonil and thiophanate-methyl are all good options, Aynardi says.
Whether you’re dealing with pink or gray snow mold, you’ll want to rake up dead turf in the spring and reseed the lawn. “You also want to rake up leaves and stuff because they’re going to act like snow; they’re going to act like a blanket,” Aynardi says.
And in the fall, don’t apply too much foliar nitrogen since that can create too much top growth. Then, when snow falls, the grass will lie fold over on itself and create that same blanket effect, Aynardi says.
Warm season grasses.
Going into and coming out of winter, spring dead spot and warm season large patch are the big issues to look out for, Aynardi says.
When it comes to spring dead spot, the soil-borne pathogen that causes it affects the roots, rhizomes and stolons of Bermudagrass. So Aynardi recommends an isofetamid to treat. “Make sure you get it in before the temperatures at a 2-inch depth are below 55 degrees at an absolute minimum,” he says. “But I like to say between 55 and 60.”
In zoysia, St. Augustine, centipede and other warm grasses, applications for large patch can be made when temperatures reach about 75 degrees for five consecutive days.
To identify it, look for patches of turf that have orange-ish or yellowish outer edges.
Penthiopyrad, myclobutanil and flutolanil are good treatment options and there are many good options on the market, Aynardi says, but be sure to include a bit of post-application irrigation to move the chemicals into the whorl of the leaves.
Over the winter.
Now is the time to take a look at your chemical program and make adjustments before the busy season hits and crews are running.
“Evaluate what did and did not work in 2018,” Giese says.“Reach out for advice on different approaches to those items that were difficult last year. Have a plan in place to make adjustments or wholesale changes in your programs for 2019. While each season doesn’t always go according to plan, creating and preparing for disease control now can be less hectic than doing it the morning of the application.”
The off-season is also prime for maintaining and updating spraying and spreading equipment, Reicher says, so check out calibration and particle distribution.
“Walk-behind rotary spreaders with a single propeller tend to throw granules heavily in the center of the pattern, then taper off to the edges in a typical bell-shaped curve,” he says. “It’s important to remember, though, that granule size and weight affect distribution – which is usually what causes the bell-shaped curve to shift right or left. Wear on the spreader will dramatically affect the distribution.”