Zane Raudenbush is a former undergraduate student of mine while he attended Rutgers Univeristy. Zane went on to conducted his graduate research at Kansas State University earning a PhD degree. Dr. Raudenbush is now on staff at Ohio State Univeristy (Wooster campus).
What Zane has done is to offer real insights into how best to discourage silvery thread moss on golf greens and best practices to manage the problem.
Golf turf managers know that moss has become more of a problem on putting greens in part do to the extremely low mowing heights demanded with the modern game of golf.
Once moss becomes established on greens it slowly crowds out the bentgrass or Poa annua turf. Bentgrass stolons have a difficult time penetrating a dense moss colony of moss.
Below are some summary points from Zane's PhD turf research conducted at Kansas State University.
First, silvery thread moss does not obtain water and nutrients from the soil as water is absorbed by the moss directly from irrigation, rainfall, or guttation -reducing irrigation frequency has been shown to reduce moss growth and spread.
If syringing greens is a part of your normal greens management plan during the growing season, it would be helpful to keep water away from moss - simply do not syringe the areas on each green with moss present.
Second, research has found that spoon feeding Nitrogen using a ammonium sulfate source will increase moss infestations - spraying soluble N every couple weeks will enhance moss growth. A urea Nitrogen source applied was reported to be not as bad as ammonium sulfate but will still encourage moss growth if sprayed every couple of weeks.
What does the above mean? Everytime you spoon feed with ammonium sulfate or urea you are feeding and encouraging moss growth. Using this information you should consider switching to applying Nitrogen to greens using an organic source.
Third, understand that moss is most competitive during the cooler temperatures of early to mid spring and during the fall months.
Fourth, recommend use of the product Quicksilver on greens, applied at the rate of 2.0 fl oz / acre, every three weeks, or a total of thirteen (13) total applications applied through out the growing season - from March through to October.
Quicksilver will reduce the competitiveness of moss, but will not completely remove it.
Keep in mind that moss, if left untouched, will crowd out bentgrass from the turf as bentgrass stolons will not penetrate a dense moss colony; therefore, available sights need to be created for the bentgrass to start to move into the moss infested areas of a green.
Fifth, research shows that all forms of aerfication treatments reduced moss cover as the aerification holes creates available sites for the bentgrass stolons to fill in the voids.
With aerification you do not have to aerify the entire green. Concentrate the aerifications on areas where moss growth is the highest. Recommend using a tine size of 3/8 inch or larger and fill the holes with sand. Quicksilver should be sprayed three to five days before aerifying to prevent moss from infesting the aerification holes.
Verticutting is also helpful to break up the moss pads to better allow bentgrass to move into the voids.
In addition to the traditional spring and fall greens aerifications suggest you add at least two additional aerifications to the moss infested areas of greens.
Best timing for the added aerificatons would be early to mid May spot aerification, using 3/8 inch tines, on areas with moss - then fill with sand. Repeat the 3/8 inch aerification to moss areas again in early to mid June.
With each aerification or verticutting would add bentgrass seed to the surface at the rate of 1/4 pound of seed per 1,000 square feet.
