Kansans growing tall fescue--the state's No. 1 lawn turf--have good odds this year for a lawn blight called brown patch disease, which can develop in just 24 to 48 hours.
"If you go out in the morning and the temperature already is in the high 60s to low 70s (F), yet your lawn is covered with dew, the conditions are ripe for brown patch," said Ned Tisserat, plant pathologist with Kansas State University Research and Extension.
Modern folklore includes the idea that brown patch outbreaks occur when a contaminated mower or other piece of lawn equipment introduces the fungus into a lawn.
"Don't believe it," Tisserat said. "Almost all lawns have plenty of brown patch fungus in the soil. There's no way to get rid of this fungus, and it can wait around in soil almost indefinitely.
Typically, the only things limiting its development each summer are the weather and good lawn management."
The state's "blemish-free" lawns tend to be most at risk. Frequent watering can keep turf leaves perpetually moist. Top-end fertilizing makes lawns lush and more susceptible to damage, the plant pathologist said.
But brown patch can be severe on almost any lawn during extended periods of hot, humid weather. The disease spreads from the turf leaves down into the plant crown. When that happens, brown patch can kill tall fescue, as well as perennial ryegrass and creeping bentgrass, he said.
In most years, however, brown patch doesn't harm crowns. It simply creates unsightly areas of dead-looking turf that can require up to a month to recover (again, depending on weather and watering).
"Fungicides aren't a very effective cure. If nothing else, you'll be applying them after the disease has caused substantial injury," Tisserat said.
Preventive fungicide applications may be worth the trouble to Kansans who want "perfect" lawns. "You have to apply them at 21- to 34-day intervals, though. The products of choice are relatively expensive, and they aren't available to the general public in small quantities. Those facts translate into your having to hire a certified lawn-care firm (yet another cost) to prevent a disease that more often than not will just cause temporary problems," he said.
The first symptoms of brown patch are irregular, water-soaked and sometimes brown-rimmed spots on leaves. What most people notice first, however, is infected turf areas' taking on a purple-green cast.
"It's similar to the color change associated with drought stress--as is the infected turf's quickly fading to a light tan or brown,"
Tisserat said. "These symptoms may show up in either irregular patches or rough circles that range from several inches to several feet across. Sometimes these patches will join to blight large sections of lawn. Newer tall fescue varieties, on the other hand, may exhibit a uniform blighting without distinct patches."
The symptoms' similarity to drought damage often inspires lawn owners to water more--which can be the worst thing to do.
"Although we can't eliminate the fungus from our soils, we can reduce the environmental conditions that favor its infecting our lawns," Tisserat said. "The first step in that is to water early in the morning, rather than in the evening. This will decrease the number of hours leaf tissues remain wet. Even if you water too often, doing so at the right time of day can make a big difference.
"Then don't over-fertilize next fall. Certainly don't fertilize while the brown patch is still active. If and when you need to seed or overseed, don't let your rate for that get too high, either."