The root of the problem

High summer temperatures have stressed turfgrass root systems to their limits, but the promise of cooler days and nights ahead doesn’t mean it’s time to relax.

The worst is over. Cooler temperatures have settled in. A break from the daily or even hourly pressure to keep turfgrass roots happy and healthy – or at least alive – is at hand.

Think again.

“A lot of courses still have budget problems and then to have a summer like this? (The superintendents) are exhausted; they’ve been doing this all summer long,” says Dr. Bruce Martin, a professor of turfgrass pathology at Clemson University. “Some superintendents think it’s about time to wind it up. But I wouldn’t go planning any September vacations just yet if I were them.”


After this year’s exceptional heat wave across much of the country, cooler temperatures alone won’t be enough to help root systems recover from this type of unbearable stress. Photo: Valent Professional Products

Summer Heat
Over the course of any summer, higher temperatures can cause considerable stress on turf below the surface – significantly weakening the plant’s root system and, in turn, increasing its susceptibility to possible disease outbreaks.

After this year’s exceptional heat wave across much of the country, experts agree that cooler temperatures alone won’t be enough to help root systems recover from this type of unbearable stress. As high-temperature records have tumbled from the Midwest to the Southeast, the pressure on cool-season turfgrasses has been compounded in different regions by torrential rains, stifling humidity or both. And the persistence of extremely high temperatures in some areas means the fight isn’t even over yet.

“We haven’t had environmental conditions that are good for normal turfgrass root growth all summer, which is really unusual,” says Dr. Derek Settle, the turfgrass program director for the Chicago District Golf Association. “We’ve been forced to do things we normally wouldn’t have to do. …. We’ve been on edge all year.”


Turf Triage
Fortunately, a number of options are available to superintendents to help reduce the risk posed by severe conditions to turfgrass roots. Increased mowing heights; strict water management; the use of fans to improve air circulation; adherence to fungicide programs (especially late-season sprays); and limiting play or even closing a course for a couple days can all help keep greens alive through this key period.

“Don’t let your guard down,” says Dr. Jill Calabro, a plant pathologist with Valent Professional Products. “Plants are still under an immense amount of stress because they’ve suffered a lot of growth and root stress and won’t fully recover until spring.”
 

Root growth in cool-season grasses improves in the fall and especially the spring. Healthy roots are often 4 or 5 inches long. But intense heat stress can cause those root systems to go into full retreat. Martin, who regularly assesses samples sent by superintendents to his Clemson office, said “they can get down to ¼ in. of functional root – or less” in mid-summer.

Hand-syringing greens each afternoon, when temperatures at their most extreme, is of absolutely critical importance if you want to keep those greens alive.

“You’re trying to put a light amount of water that then evaporates and helps cool the plant and keeps the crowns hydrated,” Martin says. “We say, ‘Keep up with the hoses.’ Check those greens every hour. If they drop the ball and miss a green, that’s it. The green checks out.”

Chicago-area superintendents, Settle says, have been scrambling to keep the upper root zones of their bentgrass greens hydrated, with near-constant hand-watering all summer. While Settle says high humidity earlier this season actually helped rather than hindered – “there hasn’t been as much wilt stress in July and August,” the falloff in humidity is now causing some real issues.

“Our superintendents are facing more disease pressure than they’ve faced in quite some time,” says Settle, adding that fairy ring and summer patch are of particular concern. “There’s been a lot more use of fungicides this year.”


Road to Recovery
As important as it is to protect turfgrass roots from undue stress, it is likewise critical to help them during the recovery process. Options here include, again, diligence in fungicide applications; increasing nutrition to the plant; light topdressing with a handheld spreader to help keep algae down and anchor new growth; and continued use of fans if humidity persists. If a superintendent is unsure about how much stress their roots are under, he should send a sample to a trusted researcher for analysis.

When root systems are at their weakest, protecting the entire plant becomes a top priority. Being stressed, the plant is more susceptible even now to diseases such as anthracnose, brown patch and Pythium root rots and root dysfunction, among others, it remains critical to adhere to fungicide programs designed to deal with those chronic diseases.

Superintendents should be applying fungicides throughout this whole period because it is critical to maintain programs now for disease protection, according to Calabro. The message is: Don’t back down just because temperatures are starting to relax. Stressed plants – especially after a hot summer – are more susceptible to disease. It takes a while for the plant to recover from the stress and get back on track to a strong, vibrant root stand for the following spring.

“Superintendents can use a broad spectrum fungicide such as Tourney to help control diseases that have persisted through the summer, especially on turf with stress-weakened, and therefore disease-prone, root systems,” Calabro says. “A September application of Tourney can clean up a wide variety of diseases, including anthracnose and brown patch, while an application later in the fall can help take down inoculum levels and delay the reappearance of key diseases until later in the spring, for example dollar spot.”

Martin, meanwhile, says superintendents can go ahead with a broad spectrum fungicide now as long as the greens are in pretty decent shape or you’ve kept them alive so far. He had made that recommendation in recent days – in comparison to some other fungicides that are not as safe. Tourney is not going to hurt bentgrass plants if they are in decent shape. Even as temperatures and humidity ease, superintendents still need to be on guard. Syringing is still important in September because weakened roots can dry out in the wind. For similar reasons, some superintendents will have to delay aerification until October.


Staying Vigilant to Spring
Even as temperatures and humidity ease, superintendents still need to be on guard. Syringing is still important in September because weakened roots can dry out in the wind. For similar reasons, some superintendents will have to delay aerification until October.

Those who use topdressing, meanwhile, should only do so once temperatures have fallen below the 90s. Even then, they should do so with dry sand incorporated with irrigation rather than with brushes to avoid bruising, Martin says.

If superintendents have managed to keep their greens alive this long, such practices will help them make it through the key weeks and months ahead as they regain lost mass. While golfers may not have been thrilled at times during this unusually long, hot summer, their appreciation will grow as your roots do the same.

“As long as they kept the crowns alive, the greens will firm up as they grow more roots in September or October,” Martin says.

Jim Masilak is an account executive at archer>malmo public relations, which represents Valent Professional Products.