Friday, January 07, 2000
of weeds to go on at Flats
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
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
"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
"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, 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.