Underwater weeds may choke off several Northern Virginia harbors this summer, unless state legislators succeed in their efforts to protect the region's fishermen and boating enthusiasts from becoming the latest victims of the state's budget deficit.

The state recently announced that budget concerns had prompted them to withdraw from a regional coalition to mow down hydrilla, an escaped aquarium plant that first began clogging the Potomac in 1983. The leafy green weed helps improve water quality, but it also tangles around boat propellers and fishing nets, and makes it difficult to get in and out of infested areas.

"In my district, I will have 14 families on welfare if they don't cut that hydrilla," said Prince William Supervisor Hilda M. Barg (D-Woodbridge). "They can't make a living fishing if they can't get their boats" to the fish.

Without Virginia's $78,000, hydrilla will not be harvested from about 44 acres in 10 locations from Alexandria to Wide Water, in Stafford County, said Giselle Bernstein, who coordinates the harvesting for the Metropolitan Washington Council of Governments. Maryland is still participating in the program and has agreed to put up $130,000 to cut boating channels at 14 places on the river.

Although the federal government matches state contributions dollar for dollar, Prince William Supervisor Edwin C. King (D-Dumfries) told the county's state legislators Thursday that local counties would have to pay the entire bill if they take over the cutting.

Northern Virginia's legislators are trying to fight the cutback. State Sen. Joseph V. Gartlan Jr. (D-Mount Vernon) has sponsored a budget amendment to appropriate about $57,000 for the hydrilla cutting.

"Harvesting this is vital to access to marinas and docking areas," said Gartlan, who lives in the Mason Neck area of Fairfax County.

If Gartlan's bill fails, it means bad news for the fisheries, marinas and swimming areas along the Virginia shoreline, particularly in Prince William and Stafford counties.

Two rainy summers in a row have reduced hydrilla's growth nearer the District, but the weed has been spreading steadily south, Bernstein said.

Hydrilla cannot grow if the water is too salty, but rain has increased the Potomac's fresh water content, allowing hydrilla to thrive there, she said.

Submerged aquatic grasses, which include hydrilla and a host of other plants, have spread from 400 acres in 1983 to more than 5,000 in 1989, Bernstein said.

"If it's a boom year {for hydrilla}, we could have a real problem on the Virginia side," Bernstein said.

Staff writer Donald P. Baker contributed to this report.