Turf Pest of the Month: How scouting for silvery thread moss can prevent bigger issues

Zane Raudenbush, Ph. D.

Silvery thread moss thrives on putting greens with cool-season turf. Putting greens, with low mowing heights, frequent nitrogen applications and intensive surface management techniques — such as brushing and grooming — create a perfect oasis for this moss to survive, says Zane Raudenbush, Ph. D., turf and herbicide specialist at the Davey Institute.

Raudenbush says the species of Bryum argenteum found on golf courses is more vigorous and well-adapted to the microclimate of a green. While most mosses need water to survive, this species can go for long periods without water.

Dew and fog can also provide silvery thread moss with the water it needs to thrive on putting greens. The low mowing height of putting greens helps moss compete with putting green turf. In other areas of the course, moss can’t outcompete turfgrass.

One thing superintendents should know and understand, Raudenbush says, is research also shows that plant growth regulators can exacerbate moss on putting greens.

“So here you have the moss that can kind of grow freely in among plants whose growth is heavily regulated and now maybe you get some ball marks, or you lose some turf to dollar spot or wilting, and the turf isn’t able to recover,” he says.

Silvery-thread moss on creeping bentgrass. (Photo: Zane Raudenbush, Ph. D.)

Moves easily

Raudenbush says silvery thread moss produces buoyant vegetative structures that can spread easily from one putting green to another. Golfers’ shoes, equipment and heavy rain events can move these structures to newer parts of the course.

“A lot of practices that disrupt the canopy and move those propagules (vegetative structures that detach from a plant to create a new one) around with things like brushing and grooming,” he says. “When you look at a quarter-size colony of moss, each one of those shoots can start a whole new colony.”

That’s why Raudenbush says it’s important for superintendents to scout for moss. He encourages superintendents to use a cup cutter and cut out those small patches before they spread.

“(Superintendents) definitely should not underestimate the value and usefulness of mechanically removing those colonies when they notice them,” he says. “It’s much easier to mechanically remove them early instead of letting them have 10 percent or 15 percent infestations, where mechanical removal isn’t so feasible.”

This field study evaluated the effects of hollow-tine aerification with drench applications of dish soap. (Photo: Zane Raudenbush, Ph. D.)

Control methods

Raudenbush says removing small patches is the best approach to controlling silvery thread moss. He says superintendents should also consider reducing water use.

“I tell people to look closely and do whatever they can do to try to keep the surface dry,” he says. “But unfortunately, it grows in places that need water.”

There are long-term results with a carfentrazone-ethyl herbicide, he says.

“The moss might have been really happy and very competitive when applying the herbicides,” he says. “Now the competition favors the grass because the moss is injured, and maybe there are some practices you can do that will encourage the grass to outcompete the moss.”

Raudenbush says he’s also seen success using soap. He says the soap also doesn’t harm the surrounding turfgrass.

“With Dawn dish soap, I was mixing it at two ounces of soap per gallon of water,” he says. “I use a watering can with a shower head nozzle, and directly apply it to the surface.”