Summer heat waves generate an array of challenges for golf course superintendents, not the least of which is turfgrass heat stress. And this heat stress can manifest itself in a big old mess of human stress for those trying to combat it.
Dealing with and prepping turfgrass to withstand heat stress, is more on a superintendent’s radar than it used to be, says Bayer Green Solutions Team member Dr. Zac Reicher. “There is no questioning the effects of climate change on our industry,” he says. “Plants don’t have as much recovery time as they used. Shorter winters. Earlier springs. Summer lasting into fall. Because of the dryness and the heat, we’re seeing more traffic on the greens throughout the year. All of this plays into the ability to fight the stress.”
Persistent intense heat events – those lasting two or three weeks and longer--- seem more common in recent years. It’s these events superintendents and turf managers struggle with figuring out not only how to get the turf through these periods, but how to do that while at the same time keeping up with the player demands for high-quality turfgrass. It’s safe to say expectations are not dropping any with the increasing temperatures. One could argue those high expectations increase right along with the temperature.
Golf course superintendents, as a whole, are not simply relying on time-tested, proven past methods for getting turf through intense heat. Out of necessity, they’re coming up with some new ones, as well.
These new strategies stem from networking with fellow superintendents, talking with their different sales reps and also paying attention to what some of the experts in the field are saying, says Mike Goatley Jr., a professor of agronomy at Virginia Tech, who is a big proponent of preconditioning turfgrass to handle these intense heat events.
“I always say, don’t wait for the stress to arrive,” Goatley says. “Superintendents know this. They are already on programs that incorporate wetting agents, plant growth regulators, bio-stimulants, etc. If you have a track record of success, you stick with it.”
Goatley cautions turf managers against going too crazy in anticipation of higher than usual temps. “I’m one who believes that letting turf get under a little stress is okay,” he says. “Often, superintendents will want to raise heights when preparing for heat. This is understandable but keep it reasonable. If you wait until midsummer to raise heights, your root system isn’t going to be strong enough.”
Preconditioning turfgrass is a trending topic when talking about heat stress. Even in the relatively mild climate of the Pacific Northwest, Shane Riley, a regional sales rep in the Seattle area for Winfield United, has witnessed a trend toward a more proactive approach to heat stress. Heat stress in Seattle obviously a different animal than heat stress in the Midwest or South, but that isn’t to say when those western Washington temps hit the upper 80’s to low 90’s they can’t be just as trying on the Poa annua as the low to mid 100’s can be for other parts of the country.
“With drier, hotter summers the new norm, what I’m seeing now from a lot of superintendents in this part of the country is the use of biostimulants to precondition -- using them Spring to Fall,” Riley says. “More and more supers are starting early and going into the middle of October here. We just didn’t use to do that in this region.”
Riley is also witnessing other strategies at play to deal with elevated heat stress. “Humic acids. Kelp extract products. Phosphites and, of course, wetting agents. Heat has become a real issue here when it never really used to be. Superintendents are finding ways to stay on top.”
Goatley advocates the use of seaweed-based extracts and offers supplemental growth hormones as a new tactic. “We’ve found these are very effective in the preconditioning stage,” he says. “Cool-season grasses in particular don’t have the ability to produce the internal hormones we wish they could. This can be effective not only before, but during heat stress, as well.”
Organic acids are effective, as well. “Fulvic acid and humic acid, on their own or used together,” Goatley says. “We have found they have significant impacts in rooting. Drought tolerance. None of these are silver bullets, of course. But they are all effective parts of good overall preconditioning program.”
Reicher is a firm believer in the pre-conditioning of the plants well before a temperature situation ever occurs. The main focus of that preconditioning is maximizing photosynthesis.
“Basically, anything we can do to maximize photosynthesis anytime of the year ... That’s where it all begins,” says Reicher. His cool-season territory runs from Indiana westward to Hawaii. Maximizing photosynthesis throughout the year allows the plant to increase carbohydrate storage and maximize rooting, which in turn, enables better heat tolerance and summer survival.
“And don’t discount the photosynthetic and plant health benefits of fungicides that contain Bayer’s Stressgard Formulation Technology, which has stood up to years of research under summer stress,” he says.
More energy production in plants increases tolerances to stress, including diseases.
Reicher’s second key in the preconditioning process ties into the first -- keeping the turf free of other stresses.
To prevent turf from going into heat stress, or, if it is starting to go into heat stress, which, despite the best efforts, is sometimes going to be the case, alleviate other sources of stress. "You certainly don’t want any other stresses affecting that plant," Reicher says. "We’re talking diseases, of course, but also localized dry spots, excess traffic, cultivation, etc. We want to keep the plants as healthy as possible.”
The practice of spoon-feeding is one of the tools superintendents must have in their arsenals in the battle against heat stress, Goatley says. “This is a major change in strategy,” he says. “Back in the day, we didn’t used to think spoon-feeding was beneficial. Spoon-feeding .05 to .15 pounds of N per thousand keeps your greens active. Keeps the grass active. “
If you do find yourself caught in some major heat stress, there are common sense practices that need to be implemented. While the situation is not ideal, all is not lost.
“There are the things most superintendents know to do when they find their turf heat stressed,” Reicher said. “Reduce frequency of mowing opting for rolling instead, maybe raise the mowing height. Don’t topdress. Obviously, don’t make a herbicide application. Basically, don’t do anything that is going to add more stress. Your focus has to change somewhat. You go into survival mode keeping the plants alive.”
Goatley agrees, and stressed use of bio-stimulants and even needle tining to improve soil oxygen levels.
Reicher also points to the growing nematode problem he’s finding on his travels, even in places like Wisconsin and Nebraska, and their correlation to heat stress. The problem here is when plants go under heat stress, every other stress or problem -- like a nematode population -- is magnified.
“It’s becoming a huge issue,” Reicher says. “The problem here is, you usually don’t realize you have a problem until it’s too late. Nematode problems will often be mistaken for any number of other issues including soil pathogens or localized dry spot, and don’t respond to water or fertility.”
Once an extreme heat even has subsided, the experts advise turf managers return to precondition mode. “I think identifying the why is important,” Goatley says. “Why did we suffer this stress? And then address for the future. More than likely this means going back to the basics … The preconditioning and planning.”
Ron Furlong is a turf writer and frequent GCI contributor.