Knock down diseases

Knock down diseases

Prevent, identify and treat common diseases that crop up in the first half of the year.

March 10, 2015

Across the country, the first months of the calendar year offer a slower pace for green industry businesses (unless you’re plowing, of course).

But now is the time to keep disease on the radar. There’s no real hibernation in landscaping. Diseases crop sooner than you might think.

Here is your guide to disease issues all across the country for the first quarter of 2015.


Spring can come as early as mid-March, or not set in until May – and even then, temperatures can stay quite cool. Still, there is disease pressure that LCOs should mind during this first quarter, and especially in April.

Red thread: Pictured above, this is one of the first diseases LCOs will spot in northeast lawns, and it can occur any time the weather is cool and wet, says M. Bess Dicklow, extension plant pathology specialist at University of Massachusetts. Ryegrass and fescues are most susceptible to red thread, and it generally occurs in poorly fertilized areas.

Symptoms include an irregular thinning of the lawn, resulting in inconsistent turf depth. “You can see the ‘red threads,’ which are actually the survival structures, with the naked eye,” Dicklow says. If red thread is pervasive, you’ll notice a pinkish path in the lawn.

“What happens is when conditions get dry, the red threads dry out and become brittle and fall into the thatch where they stay until conditions are favorable for them to become active again,” Dicklow says.

Prevent red thread with adequate fertility and determine proper nutrient levels by conducting a soil test. The ideal soil pH for turf is between 6 and 6.5, Dicklow says. “For every disease, water deeply and frequently, which means applying a lot of water once a week and not turning on your irrigation system every day and sprinkling the grass because that just encourages these fungi.”

Prevent future outbreaks of red thread by collecting mowed grass clippings, and do not pile clippings on the turf. Pruning trees may be necessary to allow more sunlight to reach turf, which lessens the cool, moist environment that diseases love. “For red thread, we generally do not recommend using fungicide,” Dicklow says.

Gray snow mold: This common northern turf disease requires snow to develop and its symptoms are brown, matted grass that tends to have a gray tinge to it. “There are sclerotia present that can be seen with the naked eye and look like peppercorns or mustard seeds,” says Dicklow.

The best snow mold preventive control happens in fall by avoiding excess fertilization. Dicklow recommends making the last nitrogen application six week before dormancy. And keep mowing as long as the grass is growing. Also, a fungicide application before the snow flies will help prevent the fungal disease.

During winter, avoid snow piles on the lawn if possible. “If you can at least spread out the snow, the area can warm up and dry out in the sunshine,” Dicklow says. “The drier weather will stop these fungi from growing.” As for treating gray snow mold, warm and drier days tend to do the trick. And, gray snow mold is rarely a long-term threat to a lawn. Come snow melt, improve drainage on the property if that is an issue. “Rake out the lawn and if the grass does not come back (in affected areas) then reseed and lightly fertilize,” Dicklow says.

Pink snow mold: Pink snow mold is active under snow cover and any time the weather is cool and wet. “Symptoms are more circular patches, and sometimes when the lawn is wet you’ll see a pink mycelium,” Dicklow says. Pink snow mold, if left untreated, can kill off turf.

The same preventive rules as gray snow mold apply here. “Pink and gray snow mold can occur together, and often do,” Dicklow says.


With warm- and cool-season grass varieties in this region, some lawns might be battling weed and disease while others (namely tall fescue) are looking their best January through March. “You may have some brown patch pop up (in tall fescue), but I wouldn’t consider that a major disease problem at that time of the year,” says Clint Waltz, turfgrass specialist at University of Georgia.

Tall fescue might respond to a few consecutive days of cold, cloud-covered weather by turning a bit brown. “But that’s a cold injury response and not a disease issue, and all it takes is a change in environmental conditions for the tall fescue to bounce back,” Waltz says.

On the other hand, southeast LCOs should keep these diseases on their radar:

Spring dead spot: As its name implies, you’ll notice spring dead spot by its 12- to 16-inch diameter spots of dead turf. Because this fungus is best prevented in fall, first-quarter treatments mainly prevent the spread of the disease, Waltz says. He recommends a fungicide application on the spot once the grass greens up.

Large patch: Large patch appears as blighted, dead or dying grass in area up to 10 feet in diameter. This disease is especially common in centipede and St. Augustine grasses as they transition into active growth in early or mid-April, Waltz says. Especially if a site has a history of large patch, April is the time for a fungicide application.

“Early spring application of a fungicide can help prevent the disease and transition the grass better or more easily, since we don’t have as much turf loss (from the disease) in the spring.”


Disease is less of an issue in the arid West and southern California than drought. Lack of water drives turf and plants into stress mode, says James Baird, turfgrass specialist at University of California Riverside. “It has been so dry here that disease has not been a problem,” he says.

Snow mold: Some northwest areas can face pink or gray snow mold, which technically doesn’t require snow to appear. Cool, wet temperatures cause the fungal disease to form in turfgrass, and the turf health generally improves with warmer temperatures and sunlight.

Photos courtesy of (top to bottom): Mary Ann Hansen; Virginia Polytechnic Institute and State University;; William M. Brown Jr.;; Howard F. Schwartz; Colorado State University;