Land managers in Southwest Colorado again this spring are combating destructive non-native flowers, shrubs and trees – arrivals from near and far that quickly wore out their welcome.
Collectively, they’re known as noxious weeds, invaders that spread rapidly, adapt to areas where soil has been disturbed and outcompete native species. They cause soil erosion and diminish forage for livestock and wild animals.
It’s hard to get them under control.
“We don’t use the word eradication,” La Plata County weed manager Rod Cook said Tuesday. “It’s generally the exception and not the rule.”
But there are success stories, Cook said. Inspections the last two years have turned up no absinth wormwood on one-quarter acre west of town where a concerted effort was made to eliminate adult seeds.
“I’d say that eradication is directly proportional to your level of determination,” Cook said.
On the other hand, Russian olive, introduced in the United States as an ornamental and for windbreak duty in the early 1900s, is an ongoing regional thorn in the side. It gets along in poor soil because it stores nitrogen in its roots, and in riparian areas, it sucks up more than its share of water and spreads rapidly.
“Noxious weeds may take over because they’re prolific seeders, they’re first up in the spring or they don’t have natural predators,” Cook said. “The oxeye daisy is an example. It spreads fast, steals water and nutrients. Not even goats eat the oxeye. Deer and elk eat around it.”
The Minnesota Department of Agriculture estimates there are 5,000 invasive species in the United States. At last count, the Natural Resources Conservation Service lists more than 70 invasives in Colorado. La Plata County has 43.
The intruders arrive in the United States, sometimes by design, for cultivation, as ornamentals or for erosion control. Others arrive as stowaways on boats, vehicles or animals. The wind brings seeds to fertile ground and people move them from one place to another on their shoes and pants or on their horses or dogs.
A fourth and final year of taking on invasive species on U.S. Forest Service land disturbed by fuel-reduction projects is underway. The goal is to locate plots, schedule contracts for treatment and monitor the results.
In 2010, the U.S. Forest Service and the nonprofit San Juan Resource, Conservation and Development Council, with $1.5 million in federal stimulus funds, began to inventory and treat noxious weeds in the San Juan National Forest where hazardous-fuel reduction work had disturbed the earth.
Seventy-seven areas were identified for treatment by chemical, mechanical or biological means in La Plata, Montezuma, Archuleta and San Juan counties.
“The methods used to minimize fire danger also disturb the ground and make for a perfect environment for weeds to move in and proliferate,” said Miles Newby, director of the program.
Funds purchased GPS units, Geographic Information Systems computer software and equipment, including trucks. The project also created 25 seasonal jobs for high school students and local weed-treatment companies.
The project so far has treated 550 of 12,000 acres in La Plata County and 3,000 of 12,000 disturbed acres in Montezuma County, Newby said. The dominant species treated have been houndstongue, musk and Canada thistles, yellow toadflax, oxeye daisy and various knapweeds, he said.
“The war on weeds is an ongoing battle, but through partnerships and appropriate management practices and education, we can reduce the rate of spread of noxious weeds,” Newby said.
In Montezuma County, the road department treats invasives along county roads and in gravel pits, program operator Don Morris said.
“Our program is entirely separate from the ARRA (American Reinvestment and Recovery Act) project,” Morris said. “But we do some contract work for the Forest Service and the BLM.”
The Southern Ute Indian Tribe operates a weed-management program through its Department of Natural Resources. In a written statement, Chuck Lawler, head of the water resources division, said: “There have been ongoing inventories of noxious weeds for well over a decade. The number in general is consistent with what is found throughout Southwestern Colorado.
“The tribe uses chemical and mechanical means for controlling noxious weeds, but it has been cautious about using biological methods. It may be, however, that some insects introduced for biological control by others have made it onto tribal lands.
“The tribe tries to work cooperatively with state, county and local governments on many natural-resource issues, including the management of noxious weeds,” Lawler said in his statement.
daler@durangoherald.com
