Grass that was genetically engineered for golf courses is growing in the wild, posing one of the first threats of agricultural biotechnology escaping from the farm in the United States, a recent study says.

Creeping bentgrass was engineered to resist the popular herbicide Roundup to allow more efficient weed control on golf courses. But the modified grass could spread that resistance to the wild, becoming a nuisance itself, scientists warn.

"This is not a killer tomato, this is not the asparagus that ate Cleveland," said Norman Ellstrand, a geneticist and plant expert at the University of California, Riverside.

But Ellstrand noted the engineered bentgrass has the potential to affect more than a dozen other plant species that could also acquire resistance to Roundup, or glyphosate, which he considers a relatively benign herbicide.

Such resistance could force land managers and government agencies like the U.S. Forest Service, which relies heavily on Roundup, to switch to "nastier" herbicides to control grasses and weeds, Ellstrand said.

The bentgrass variety is being developed by Scotts Miracle-Gro Co. in co-operation with Roundup's manufacturer, Monsanto Co.

Jim King, a spokesman for the Ohio-based Scotts, said seed from a test plot escaped several years earlier while it was drying following harvest in the Willamette Valley, home to most of the U.S. grass seed industry and the world's largest producer of commercial grass varieties.

The study was completed by U.S. Environmental Protection Agency scientists based at Oregon State University. Spokesmen for both companies said they had been expecting the results, to be published in the journal Molecular Ecology.

"We've been working to mitigate it," said King. "Now we're down to maybe a couple dozen plants."

The engineered bentgrass is under review by the U.S. Department of Agriculture, which published a paper in June that assessed the threat but did not reach any conclusions — leaving that for an environmental impact statement being prepared by the department's Animal and Plant Health Inspection Service.

But the USDA review paper noted that glyphosate is "the most extensively used herbicide worldwide," and that creeping bentgrass and several of the species that can form hybrids with it "can be weedy or invasive in some situations."

In 2003, the International Center for Technology Assessment in Washington, D.C., filed a federal lawsuit seeking to halt development of genetically engineered bentgrass. The lawsuit is still pending, a USDA spokeswoman said.