The summer of 2025 will be one to remember for many superintendents — but for some it will be for all the wrong reasons.
What began as a cool, wet extension of spring that stalled turf growth and activity early in the golf season, quickly turned into a hot, humid — and still wet — summer prime for a smorgasbord of common turfgrass diseases.
"Summer of 2025 has been a pathologist's dream," said Kevin Frank, Ph.D., of Michigan State University. "We've seen it all — epic dollar spot, brown patch, anthracnose and various Pythium diseases."
Frank published a primer earlier this summer on how superintendents can beat the heat.
David Huff, Ph.D., turf breeder at Penn State University, said turf plots in State College and golf courses throughout Pennsylvania are experiencing many of the same problems Frank has been seeing in Michigan.
"Bentgrass here didn't wake up here until June," Huff said. "When the plants needed the roots, they weren't there. They were stunted."
I was out playing nine holes the other day and thought the simplest explanation to turf maladies this summer is probably simply explained with one word — weather.
Brown patch in the state largely has come and gone, Huff said. The second half of summer, he noted, has become the season of anthracnose.
Caused by the fungal pathogen Colletotrichum cereale, anthracnose is a stress-induced disease found on annual bluegrass and creeping bentgrass putting greens. The pathogen overwinters in a state of dormancy waiting for the right time to emerge, which can be:
- through winter under wet, mild conditions
- during periods of extended overcast conditions in late spring
- under hot, humid summer conditions.
Annual bluegrass is especially susceptible, although it can be found in creeping bentgrass, Kentucky bluegrass, fine fescues, perennial ryegrass and Bermudagrass.
Symptoms can vary and often first appear as yellowing turf in irregular patterns that range in size from an inch to a foot in diameter.
Huff and Tom Bettle, a former superintendent and manager of Penn State's turf research farm, recommend a seven-day fungicide program for anthracnose control.
"Generally on native Poa, you need to go every seven days," Huff said. "When you don't, we're seeing (anthracnose) come back after 10 days."
It has been much the same in Michigan.
"High temps and humidity started relatively early for us — around the summer solstice — and have persisted with few breaks the entire summer," Frank said.
"Most of the state has at various times had too much rain while a portion of western and central Michigan have been approaching low level drought classification.
"I was out playing nine holes the other day and thought the simplest explanation to turf maladies this summer is probably simply explained with one word — weather."
For areas that have not received enough moisture, Frank recommends syringing hot spots at the hottest time of the day.
Bentgrass here didn't wake up here until June. When the plants needed the roots, they weren't there. They were stunted.
It is commonly perceived that noon is the warmest part of the day, when it is often around 4 to 6 p.m., he wrote early in the summer. Syringing late in the afternoon might make the difference this year between healthy and heat-stressed turf.
Both Frank and Huff recommended applications of nitrogen in the battle against anthracnose.
"Fungicide programs should be at the full rate, and superintendents should add nitrogen to their tank mix at about a half-pound (per 1,000 square feet)," Huff said. "Superintendents are under pressure to produce (green) speed, so many won't want to do that, but a boost of nitrogen will help with anthracnose."
For more information on managing common fungal diseases in turf, download the Chemical Control of Disease guide published by the universities of Kentucky and Wisconsin and Rutgers University. Or, click here for information from North Carolina State University on managing anthracnose.
There could be another tool in the Poa-growing superintendents' arsenal for the fight against anthracnose. Huff devoted much of his career to developing PA-33, the first commercially available seeded variety of Poa annua.
Summer of 2025 has been a pathologist's dream. We've seen it all — epic dollar spot, brown patch, anthracnose and various Pythium diseases.
Huff recently completed his second harvest of PA-33 seed, and for the second year, he has sold out of his admittedly limited inventory.
On test plots and the PSU nursery where it is grown, PA-33 has shown to resist anthracnose on a 14-day fungicide program.
"With this new variety of Poa," Huff said, "we've been able to go every 14 days and not have any problems with anthracnose."
Huff harvested seed from about 5 acres last year. This year, he harvested about 3 acres. He plans to expand the operation next year with an additional 6 acres under production.
The offspring of Poa supina (father) and Poa infirma (mother), PA-33 thrives under aggressive management. Neither parent can tolerate close mowing, but together, their offshoot thrives under when mowed under one-tenth of an inch.
"Most of the seed has been reserved by repeat customers from the first harvest," Huff said. "I'm starting to tell people we don't have seed for them, and I don't want to have to do that."
