It’s silent, it’s sneaky and it’s virtually undetectable to the naked eye.
But more turfgrass managers are taking a closer look at their overseeded golf courses and discovering that what first appears to be water-soaked or yellow spots is actually a new disease that can weed out acres of overseeded, cool season turf.
Chytridiomycetes is a fungal disease caused by a single-celled leaf organism that grows inside the leaf cells of turf plants. Golf courses and other stressed or high-salt soils are prone to the disease, which has since spread to nine states including California, Arizona, the Carolinas, Texas, Colorado, Nevada and Florida. Tagged “rapid blight,” the disease shows up most often in late fall and winter, primarily October through December, and seems to be more prevalent in areas irrigated with reclaimed or poor quality water, noted Wendy Gelernter, research director, PACE Turfgrass Research Institute, San Diego, Calif.
Though Gelernter said the Turfgrass samples she has tested so far originated from golf courses, landscape contractors should familiarize themselves with the symptoms and understand possible treatments. “It doesn’t hurt for contractors to be aware that there is a new disease and it shows up in overseeded turf, and if they have an unexplained problem this could be it and they should contact a diagnostic lab,” she said.
VITAL STATS:
The Beginning. Chytridiomycetes was first discovered on Poa annua greens in California in 1995. “We did the diagnostics in our lab and we kept getting things that looked like this and that, but nothing was working to treat it,” Gelernter explained.
A few years later, researchers noticed the disease in Arizona and Nevada on overseeded fairways. The fungus appeared on overseeded perennial ryegrass and Poa trivialis and soon it also appeared on golf courses in the Southeast. “That’s when more people began to pay attention to it – it was an oddball before then,” Gelernter said.
Now, the disease is prevalent in nine states, all reports stemming from golf courses, and has been proven to also destroy bentgrass as well.
The Symptoms. Rapid blight might have earned its moniker because it spreads before professionals catch it. Unlike other disease that leave visible trademarks on turf, like mushrooms on fairy ring, chytridiomycetes infests inside the leaf and under a microscope it looks like football-shaped objects living inside plant cells. Turfgrass managers might notice irregular, yellow spots or water-soaked spots on leaves.
“This disease does not produce outside structures on the plant,” Gelernter identified. “Everything happens on the inside. There is really no evidence that there is a fungus operating unless you look under a microscope.”
The disease hits during cooler or humid weather, most often in the late fall and winter, and so far seems to be contained to managed turf areas. Golf courses with high soil salts and low-quality water seem to be more susceptible, Gelernter notified. Topdressing might cause turf to be more sensitive to the disease since the sand agitates and abrades the leaves, she added.
Preventive Measures. A 2001 report on the disease identified the fungicide mancozeb (found in products loike Fore, Dithane, Mancozeb, Protect and Pentathlon) can prevent the development of the chytrid disease. If applied before disease sets in, this treatment may slow or stop its spread.
Also, keep soil salts below 3 dS/m with regular salinity monitoring and leaching programs, as the disease seems to be linked to areas with a build-up of soil salts, the report suggested. Turfgrass managers should avoid sand top-dressing if tuf shows sings of stress or disease symptoms.
Curative Measures. A combination of mancozeb plus trifloxystrobin can stop further development of symptoms after the rapid blight is detected.
Additional Notes. While incidences of rapid blight have increased substantially in recent years, Gelernter said this might be because the disease is in fact spreading – or because people used Fore more prominently in their treatment programs in the past and were unknowingly preventing the disease. “What it looks like is that it is a new disease and that it is, in fact, occurring I more places as time goes on,” Gelernter concluded.
While she said that landscape contractors should not scrutinize their properties for this disease, as it has been predominantly reported from golf courses, if they have recently overseeded a property and notice these symptoms, they should consider sending a sample to a laboratory.
“My guess is that in non-golf situations the disease is less likely to occur because the turf isn’t quite as stressed,” she noted.
Note: For more information on the disease, log onto www.pace-ptri.com and download the report filed under “diseases.”
The author is Managing Editor – Special Projects for Lawn & Landscape magazine and can be reached at khampshire@lawnandlandscape.com.