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John Reitman

By John Reitman

Producing healthy turf is a multi-pronged strategy


Jim Kerns, Ph.D., of North Carolina State.Each time he is invited to speak on someone else's turf, Jim Kerns, Ph.D., makes it a point not to be what he calls a "seagull pathologist."
"That's someone who flies in, makes a lot of noise and leaves a lot of crap," said Kerns, a turfgrass pathologist at North Carolina State University, during this year's Ohio Turfgrass Foundation Conference. "And I don't want (Ohio State pathologist Joe) Rimelspach to have to go clean it up."
When he was asked to speak on a hot-button topic like "the influence of fungicides on turf health," Kerns decided, thankfully, to simplify matters, changing his presentation to a more general "maximizing turf health." Besides, as Kerns noted, a lot more than just fungicide is required to produce a healthy turfgrass plant.
Weather, cultural practices, mowing heights and drainage all play an important role in growing and maintaining healthy turf.
"For a pathologist, I still get that geeked out moment when I walk up and everything is dead," Kerns said. "The fun part is the challenge of helping you to fix that.
"The things that kill turf fastest are soil, you and Mother Nature. Disease is a distant fourth. It's not that they're not a problem, but we have to keep in mind that sometimes fungicides are not going to help us."
For 60 minutes, Kerns provided some quick tips that when used in concert with the right fungicides, can help maximize turf health. And much of the hour was spent discussing sand.
"Any time I make a site visit, I pull a plug and hope to see the crown buried in sand a quarter-inch below the mow line," Kerns said. "That's an indication of a good topdressing program."
Although some superintendents are able to topdress throughout the summer, many, at least in North Carolina, cease in late summer. That is a mistake, Kerns says, especially when there is no overnight break from extremely hot summer conditions.
"You can topdress all summer long, and it's not going to have an adverse affect," he said. "Yes, you might have to skip that 100-degree day, but you don't have to stop, because conditions can go backwards very quickly when you get those really warm days and warm nights."
He suggests light and frequent topdressing every two to four weeks.
"I think this is the most important thing we can do to make sure our fungicide program works well," he said. "We are helping water infiltrate the system and it keeps it away from the crown. You will see a vast difference if you commit to a program like this now. In the summer, you'll see things you've never seen before.
"The guys in North Carolina who do this rarely see me."
His claims are supported by anthracnose research conducted at Rutgers University that showed light topdressing brushed in every 14 to 28 days not only helped prevent disease, but also modified the thatch layer, helped provide a smoother putting surface, protects the crown of the plant and provides additional protection through the winter months.
Since the groundbreaking work at places like Michigan State and Tennessee on the benefits of lightweight rolling, it's no secret that rolling more and mowing less can help promote healthier turf. Kerns said superintendents doing that should also consider slightly rising the height of cut. The effect on ball-roll speed will be minimal, he said, but the difference in turf quality will be significant.

For a pathologist, I still get that geeked out moment when I walk up and everything is dead," Kerns said. "The fun part is the challenge of helping you to fix that."


"Slight increases in mowing height could be the difference between a fungicide program working, or not," he said. 
"You might lose some ball-roll speed, but what you make up for in plant health is worth it when you consider (putting on) dirt is really fast."
Because of the inconsistencies achieved when setting mowing heights, Kerns said he never leaves home without a prism gauge, and suggested superintendents do the same.
"Mowing is the single biggest stress we place on turf," said Kerns, who had extension data to back up his statement. "I spend 80 percent of my time with you guys in golf, and the other 20 percent with sports, sod and homeowners. Why is that? Mowing height."
Just as important are limiting shade cover, especially on warm-season turf and slight increases in nitrogen.
"There was a time when we were applying 6 to 7 pounds of N per year," Kerns said. 
"I'm noy asking you to go up a pound, or two, or three or four. There is 10 to 12 years of research that shows if N rates were between .125 and 1.25 per 1,00 square feet per month per year, it had no effect on ball roll. What I'm asking is if you are at a tenth of a pound per week or every two weeks, they go up to an eighth. You're not going to see a dramatic decline in ball, but you're going to see a dramatic improvement to combat disease."
He also suggests using a growing degrees day model, like the one developed by Nebraska's Bill Kreuser, Ph.D., to track plant growth regulator applications.
Likewise, the benefits of aerification, whether it involves pulling a core or not, cannot be overstated.
"The more you can pull cores, the better you'll be," he said. "Pathogens thrive when soil becomes anaerobic."
Those who come from Roch Gaussoin's school of solid tining without pulling cores also can achieve great benefits, Kerns said. 
That can include cooling the soil by allowing air in.
"If you punch holes every few weeks, it's like an apple a day: It will keep the doctor away," Kerns said. "It's not that labor intensive when you think of the difference vs. core aerification, and you're going to reap the dividends because you're going to keep that soil temperature down more than somebody who isn't doing it."
If, after trying all of this, turf still is under stress, Kerns said don't cut corners when it comes to sending samples to the lab.
"Our diagnostics lab usually receives about 500 samples a year. This year, we're at about 660 to 670, and the year's not over yet," Kerns said. "And 53 to 60 percent of what we see is not disease.
"If you want us to be accurate, submit and give us the most information you can. That's the key thing with making a diagnosis; it's an art."


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