Region faces noxious weed onslaught
Drought, development and fires open door to invaders

Musk thistle blossoms cover the roadside along Florida Road just east of town on Tuesday. The plant is not native to the area and as such, has no predators, which allows it to grow and spread unchecked. Although the most recognizable invader in the county, Rod Cook, La Plata County weed manager, said there are other noxious weeds that are far more worrisome for the local region./Photo by Todd Newcomer.

A t first glance, the yellow centered daisy almost passes as a wildflower. But a deeper look at an area like Needles or Durango Mountain Resort reveals a vigorous, almost cancerous spread of the plant. In fact, the attractive oxeye daisy, a noxious weed, exists in abundance throughout La Plata County.

"To me, that's the trait of an aggressive weed," said Rod Cook, La Plata County weed manager. "It can grow in a variety of elevations and degrees of moisture and temperature. I've seen oxeye daisy above treeline near Molas Pass, growing out of shale in Ridges Basin and growing out of pine needles in stands of ponderosa pine."

Cook also has bigger concerns than just getting a grip on the spread of oxeye daisy. A major invasion of weeds of all types has come on the heels of the last five years of drought in Southwest Colorado. And while invasive weeds may seem to be spreading unchecked locally, so is local awareness. Cook and others see a bright future for La Plata County as it works to stem the spread.

Noxious weeds are plants that are not native to the region and consequently have no natural predators. They either arrive as seeds riding on clothing, vehicles, wind or pets or are sold as ornamentals by some nurseries and garden centers. Once established, they are difficult to eliminate. In addition to gobbling up thousands of acres, noxious weeds also squeeze out natives. Of Colorado's 3,000 native plant species, approximately 500 have already been displaced by the spread of weeds. Although this statistic may seem alarming, Cook said that Colorado is actually in much better shape than many Western states.

"We're not in the same bad way as a lot of other states," he said. "The spread of weeds is unbelievably vast up in places like Western Montana and Idaho."

However, things are also particularly difficult for Southwest Colorado at this point of major housing growth and limited rainfall. The lingering drought has failed to sustain native species and opened the door for invaders, according to Cook.

An unusual ally in the war against weeds

Tired of digging up musk thistle by the roots? Help could be on the way from a surprising source. The recent return of moisture to the region has also brought the return of the seed head weevil, an insect that was introduced in the early 1980s to feed on thistle. It had been presumed that drought eliminated the bugs, but numerous egg cases have been observed this season.

Rod Cook, La Plata County weed manager, said, "It took 20 years for the number of bugs to grow to the point where they were effective. Then in 2002, they crashed. That's why we're now seeing thistles that are 6 and 7 feet tall all over the county."

The seed head weevil feeds exclusively on the musk thistle seeds during its larval growth stage and destroys most of the seed production. The reappearance of the bugs appears to be a natural recovery response, but they also need a little help.

Cook explained that shoveling thistle, disposing of flower heads or spraying adult thistles will interrupt the weevils' life cycle and ultimately lead to more musk thistle. Instead he encouraged people to leave the adult thistles and weevils alone during the summer and control the new thistle rosettes, next year's plant, during September and October.

"The weevils may come back in just a few years if we have favorable conditions," Cook said.

"The challenge for this office has been educating new land owners and working to deal with weeds in a drought situation," he said. "A drought always increases the frequency of weeds. We've been dealing with this drought since 1998, and we're going to have to pay for it for a long time."

Cook explained that the drought and earthwork are similarly attractive for invasive weeds. In both cases, existing life is erased from the land and traveling or dormant seeds have an easy time getting established.

"There are voids in the vegetation and nature abhors a vacuum," Cook said. "It's going to fill it with something, and it's not always desirable. Weeds are just a symptom of something that's happened on the land."

Nicole Smith, program director for the San Juan Mountains Association, explained that fire is another form of disturbance that is attractive to weeds. She pointed to sections of public lands burned during the 2002 Missionary Ridge Fire and a section near Lemon Reservoir that burned at an earlier date.

"You would always hope that with rehabilitation efforts, the natives would come back," she said. "But with disturbed areas, the weeds have also come in quickly."

Cook said that the most recognizable weed for residents in La Plata County is the Musk Thistle. He added that although it seems unpleasant, it is also relatively easy to eliminate.

"The Musk Thistle is the one that everybody objects to and the one I get the most calls about," he said. "Then I usually go out for a site visit and show them some others that are bigger problems."

Citing bigger problems, Cook explained that in western La Plata County, Russian knapweed, a serious noxious weed that is also poisonous to livestock, is a growing problem. Leafy Spurge, the most serious weed threat in the state, is getting a foothold in the southern areas of the county. Oxeye daisy has spread throughout the northern end of the county. And yellow toadflax, a snapdragon that was introduced as an ornamental, has spread vigorously through areas like Wildcat Canyon.

However, people are also beginning to understand the problem and getting serious about managing weeds throughout the county. Smith noted that SJMA has been actively working to educate people through weed walks and weed school.

"We've been focusing on public education on weeds and trying to create a general knowledge about them and the impact they can have on public and private lands," she said.

Smith added that awareness in La Plata County is actually quite strong. "I'm impressed by how many people are aware of the noxious weed problem," she said. "And I think awareness is the first step toward dealing with the issue."

Cook agreed that local people are definitely concerned about stemming the local spread of weeds. "I think we have a high level of interest," he said. "I get a lot of calls in this office every day, and I do a lot of site visits."

And while Cook said that eradicating noxious weeds can be difficult, there are many signs of hope. As an example, he pointed to a local woman who purchased 40 acres that was infested with leafy spurge, spotted knapweed, Russian knapweed, yellow toadflax, musk thistle, Canada thistle and a wide variety of mustards.

"She went after it with a vengeance," he said. "Not long ago, I got a call from her and she asked me to come out and have a look. She had virtually cleaned it up by herself over a five-year period."

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