Turf talk -- Controlling seashore paspalum
Is there any control available for seashore paspalum in bermudagrass? It has infested our fairways and is encroaching on our greens.
Good luck. Paspalum vaginatum is one of the toughest warm-season grasses to kill. Fortunately, its a very good turfgrass for golf courses -- good enough that the LPGA returns each winter to play a paspalum-infested course in Hawaii.
"We're actually not concerned about it," says Steve Swanhart, superintendent at Kapolei Golf Course on Oahu Island. Since 1996, the course has been home to the Cup Noodles Ladies Hawaiian Open. "It's a better grass than the bermudagrass," he adds.
In fact, the course staff recently gave up on the Tifgreen bermudagrass that had struggled there since construction, and they planted seashore paspalum everywhere it had not already taken over. The initial paspalum infestation was planted unintentionally in 1992 with the Tifgreen stolons, Swanhart says.
However, some stands of seashore paspalum may be unattractive, especially if mixed with bermudagrass.
Experts claim that some herbicides might control it in bermudagrass if the grass is attacked repeatedly. Swanhart tried all the chemicals but found they also damaged the bermudagrass -- and the seashore paspalum recovered more quickly.
"When we were doing the herbicide applications, it seemed to give paspalum the edge," he says.
A prominent advocate for seashore paspalum, Ronny Duncan, Ph.D., of the University of Georgia, suggests that a one-two punch approach might work. He says that you could weaken the seashore paspalum with Asulox (asulam) or Trimec Plus -- which contains 2,4-D, dicamba, MCPP and monosodium methane arsenate (MSMA) -- then hit it with a different herbicide chemistry before it recovers from the initial burn-down.
Do the one-two punch again a month later. Repeat on a fairly rigid schedule, otherwise the paspalum will rebound -- with a vengeance. Each month, the second herbicide must be of a different class than the first herbicide, Duncan says. Follow label directions to minimize damage to the bermudagrass. Eventually, the paspalum may be dead, and perhaps the treatments can then stop.
Research in the 1980s by Ali Harivandi, Ph.D., of the University of California, indicated that MSMA, DSMA (disodium methane arsenate) and Trimec Plus were each phytotoxic to seashore paspalum. Otherwise, almost all the herbicides were fairly harmless to paspalum.
Seashore paspalum cultivars sold in the '80s have proved tough to remove from golf courses, in part because the species' waxy leaf coat repels most herbicides. The grass evolved on duned tropical beaches, where it developed fast-growing roots that can quickly seek water deep in the ground. It can extract nutrients from salty sea-side groundwater and salt spray, so it requires remarkably little supplemental nitrogen to thrive.
"If you evolve in a stressful environment, you're going to develop mechanisms to resist anything that comes your way," Duncan says.
Seashore paspalum's salt tolerance makes it attractive on tropical seaside golf courses and in cities where golf course irrigation comes from wastewater plants. The grass is likely to become more widespread as Duncan continues developing improved cultivars that will reach the marketplace over the next decade.
-- Mark Kind, GCM technical editor
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