Battling a prolific pest

Weeds: State biologists are fighting the latest outbreak in the upper bay of the noxious water chestnut.

June 01, 2000|By Joel McCord | Joel McCord,SUN STAFF

SHALLCROSS CREEK -- It's almost surreal to watch a watercraft built like a cross between a Mississippi side wheeler and a Nebraska corn harvester working its way back and forth across this Eastern Shore creek, ripping out aquatic plants.

These aren't the kinds of plants Chesapeake Bay scientists look for as indicators of the estuary's health. They are water chestnuts, an invasive species that forms thick rafts of leaves on bay tributaries, making it difficult to maneuver a canoe and all but impossible to get a powerboat through. Worse, it keeps sunlight from reaching the underwater grasses that are crucial to the health of the bay.

This craft, a marine harvester on loan from the U.S. Department of the Interior, usually can be found keeping aquatic plants out of the C&O Canal at Great Falls.

The harvester, which also bears some resemblance to the craft that clean trash from the Inner Harbor, moves slowly through the shallow water, its conveyor belt pushing a cutting blade along the bottom and two other blades, one on each side.

State scientists missed this crop in a cove on the Kent County side of the Sassafras River during a $13,500 campaign last spring to clear the plant from the tributaries of the Sassafras and the Bird River on the Western Shore.

"By the time we found out about it [last year], it was too late to do anything," says Dave Goshorn of the Department of Natural Resources. "The seeds had already germinated and we would have done more harm than good if some of the plants floated off into the river."

Mike Naylor, a DNR biologist, spotted the plants with the diamond-shaped leaves last week during a helicopter flight over the Bird and Sassafras to determine whether new plants had cropped up over the winter.

The helicopter hovered at less than 300 feet as Naylor leaned out a rear window with a camera strapped around his neck, snapping pictures of Owens Creek off the Bird and Lloyd and Turners creeks off the Sassafras.

He saw scattered water chestnut plants in most of the tributaries, but mostly he saw water lilies, a native plant that does little damage even though it forms a carpet on the water's surface much as water chestnuts do. Then, as the chopper dipped toward Shallcross Creek, he spotted the water chestnuts.

"Oh, my. We've got our work cut out for us," he said.

These aren't the crunchy delicacies found in Chinese food, but noxious weeds with spiked seed pods that can puncture flip-flops. They are believed to have been introduced to the United States from Eurasia as decorative plants in the late 1800s.

Since then, they have reproduced exponentially.

Each rosette of leaves floating on the surface can produce 20 of the five-sided seed pods that look like medieval weapons with sharp spikes. And each seed pod can produce 20 more rosettes.

They 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 the shoreline. The federal government spent the equivalent of $3 million in 1999 dollars to eradicate the plant.

It isn't clear why the plants reappear, but they were seen in the Bird River and elsewhere in the upper bay in 1955, 1962, 1964 and last year.

Eradication efforts have little time between when the plants appear on the surface in May and when the seed pods develop in June, Goshorn said.

The harvester cutting plants and churning up mud yesterday will be on the Eastern Shore most of the rest of this week, then will be loaded onto a truck and hauled to the Bird River next week. The cost of this cleanup is minimal -- a couple of nights in a hotel for the harvester's crew -- compared with the cost of last year's, said Goshorn.

The Department of the Interior isn't charging the state for the use of the harvester, and the State Highway Administration lent the DNR one of its trucks to haul the harvester.

"They really bailed us out," Goshorn said.

The DNR also is asking for volunteers for cleanup efforts on both sides of the bay.

The cleanups are scheduled for June 9 and 10 on the Sassafras and June 23 and 24 on the Bird River. Volunteers, who are welcome to bring their canoes and kayaks, should call the DNR in Annapolis at 410-260-8630 for information.

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