Battling a natural enemy

Effort: The state Department of Natural Resources hopes an ambitious eradication program will take the bite out of the water chestnuts.

May 26, 1999|By Joel McCord | Joel McCord,SUN STAFF

Water chestnuts, not the ones you get at a Chinese restaurant, but noxious plants with spiked seed pods that can cut through a flip-flop, have reappeared in Chesapeake Bay tributaries, threatening to choke off the waterways.

The plants, believed to have been introduced to the United States from Eurasia in the late 1800s and first seen in the Potomac River in the 1920s, have nearly covered Owens Creek off the Bird River in Baltimore County and Lloyds Creek off the Sassafras River on the Eastern Shore, according to John Surrick, spokesman for the state Department of Natural Resources.

The five-sided seed pods, which look like something out of a "Star Wars" movie, burrow into the mud with spikes sticking out on four sides, puncturing the feet of anyone who wades through. The pods send out shoots that turn to broad, green leaves much like water lily pads on the surface, cutting off sunlight for native underwater vegetation.

Thick rafts of water chestnuts can make it difficult to maneuver a canoe through the water and all but impossible to get a power boat through.

"That stuff gets like twine," said Ken Guleta, who lived on Owens Creek during the last infestation in the 1960s. "It wraps around a propeller and you can't back it off no way."

It isn't that the plants -- known to scientists as Trapa natans L. -- have no value, said Mike Naylor, a DNR biologist, but "the native aquatic vegetation has greater value."

DNR is planning an aggressive eradication campaign, using underwater mowers and volunteers to pull the plants out of the water in hopes of nipping the infestation before the pods burst in mid-July, spreading seeds even farther, Surrick said.

The department will turn to herbicides if necessary, he added. "But we know that's a concern and we want to avoid it."

Using herbicides could be controversial because longtime residents blame the herbicides used to rid the river of water chestnuts in 1964 for the loss of sub-aquatic vegetation.

Scientists, however, say Hurricane Agnes in 1972 did more damage to the bay than any herbicides, and a 1962 study by the Virginia Institute of Marine Science found that 2,4-D, the herbicide Maryland's DNR would use, did not harm native plants or fish.

Ronald Dahl, who has lived in a white frame house on the creek since 1973, first spotted the plants three years ago, but didn't know what they were. This spring, when they nearly covered the creek, he called DNR.

"If I'd have known what it was, I could've gone out there in my little canoe with a couple of the kids and scarfed it right up," Dahl said. "Could've done it in one load on the canoe. But now "

The plants growing in Owens Creek are related to the ones you get in a Chinese restaurant, and they have a nut that is edible, Naylor said. But the labor to extract the nut costs more than the food value.

Water chestnuts were commonly used as decorative plants in goldfish pools on the Mall in Washington in 1900, according to a 1964 report by Charles K. Rawls, a research associate at the Chesapeake Biological Laboratory in Solomons in Calvert County.

Water chestnuts were found in Oxon Run on the Virginia side of the Potomac in 1923 and over the next decade spread to cover 10,000 acres of the river along about 100 miles of shoreline.

Bathing beaches were unusable, the value of waterfront property plummeted and there were fears of encephalitis outbreaks because water pools in the leaves and provides a breeding area for mosquitoes, Naylor said. The federal government spent the equivalent of $3 million in 1999 dollars to eradicate the plants.

Water chestnuts can grow in up to 16 feet of water and thrive in lowsalinity, Naylor sad. They appeared on the shallow Bird River and other places in the upper bay in 1955, 1962 and 1964, Naylor said.

Scientists aren't sure why the plants reappear, Naylor said, guessing previous eradication efforts weren't as successful as they thought and that seeds lay dormant until conditions were right.

"We thought we did a good job getting rid of them the last time, but here we go again."

DNR has scheduled a meeting at 7 tonight at the Galena Fire Hall on Route 290 on the Eastern Shore, and at 7 p.m. tomorrow at Chase Elementary school in Chase to explain the eradication program.

Pub Date: 5/26/99

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