Friday, January 07, 2000

Spraying of weeds to go on at Flats
CU prof says herbicide killed more native plants than intruders

Colorado Daily Staff Writer

Encouraged by what they say are "exciting" results from last spring's pesticide spraying, officials at Rocky Flats say they plan to continue their aerial attack on noxious weeds in the plant's buffer zone next spring.

Herbicide opponents, meanwhile, say the results of the spraying aren't really that impressive.

A survey conducted by plant botanists indicates that the herbicide Tordon 22k, which was sprayed by helicopter over approximately 1,500 acres of the 5,800-acre buffer zone, killed a greater variety of native plants than non-native plants.

The intent of the spraying -- the first-ever aerial application carried out at Rocky Flats by the Department of Energy, which owns the site -- was to combat non-native weed species. Diffuse knapweed and other unwelcome plants are threatening to choke native vegetation in the buffer zone, which is home to several rare prairie ecosystems, site officials say.

CU biology professor Tim Seastedt, a frequent critic of the use of herbicides, said the results confirm his concerns about the effectiveness of spraying. He noted that the herbicide killed individual plants belonging to 18 different species, compared with just 10 non-native species.

"The question is, What's been gained?" Seastedt asked.

But Rocky Flats officials defended the results.

Jody Nelson, a botanist working at the site, said the higher number of affected native species was to be expected, because some 80 percent of the species on the site are native.

Site officials say all of the affected species -- native and non-native -- will rebound, but that the weeds will come back more slowly.

"The plants that we're trying to get rid of are much more highly sensitive to (the herbicide)," said Marcia Murdock, the plant's senior ecologist.

Nelson also pointed out that in addition to the plants that were killed, several other species suffered lesser effects or no effects at all.

It will take several applications to control the weeds, Nelson said, but in order to give the native plants time to rebound -- and hopefully "overshadow" the weeds -- the same areas won't be sprayed each year.

Seastedt, meanwhile, said the effects of such repeated sprayings are mostly cosmetic, because they're not going to permanently eradicate any weeds.

"It treats the symptoms," but not the cause of weed infestation, Seastedt said.

Seastedt, the Sierra Club and several other groups wrote to the DOE last year to discourage the use of herbicides, expressing concerns not only about the effects on native species but also about the risk that herbicides may migrate and contaminate groundwater.

Nelson, meanwhile, noted that herbicide application is only one of several weapons being used in the battle against weeds at Rocky Flats. Botanists are also using such means as mowing, hand-pulling, controlled burns (which have also caused some controversy due to fears that plutonium in the soil will be released), insects that eat weeds, and planting of native species.

In addition, they continue to study results and research from other weed-control sites, Nelson said.

"We're in communication with other folks to try to learn what's working," he said.