From: Ananda Shorey, Associated Press
Published April 12, 2005 12:00 AM

Sheep and Insects to Help Kill Exotic Weeds in Arizona Forests

WILLIAMS, Ariz. — Three of Arizona's national forests will soon be providing a smorgasbord for weevils, flies, moths, beetles and sheep.


The critters are expected to be sent in as early as this summer to munch on dangerous and invasive weeds that are harming endangered and threatened native plants and wildlife.


The feast is part of a U.S. Forest Service plan to treat 25 species of weeds on 135,000 acres of the Coconino, Kaibab and Prescott national forests in northern Arizona over the next 10 years.


Forest officials also will be spraying, mowing, burning, hoeing, pulling and digging to control the invasive weeds. Implementation is set for June 1.


The goal is to contain or control 14 invasive species and to eradicate eight species that are threatening the biological diversity of the area. They also want to prevent new plants from becoming established.


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"These nonnative weeds are threatening the ecosystem so much that the native species that depend on them are disappearing," said Dave Brewer, one of the plan's main authors.


The invasive weeds pose a threat to nine plant species, seven types of fish and eight species of animals that are listed as threatened or endangered. Affected species include the razorback sucker and Little Colorado spinedace fish, the Mexican spotted owl and the bald eagle.


Leafy spurge is the worst offender, Brewer said. The roots of the perennial herb can extend more than 30 feet deep and laterally. A milky latex found in the weed causes lesions on cows that eat it.


"That is the absolute most dangerous," Brewer said. "It can take over the native population at a fast rate."


The largest opposition has come from people with chemical sensitivities who are concerned about their ability to use services and enjoy recreational opportunities in areas that are being treated, Brewer said.


The noxious and invasive weeds -- especially bull thistle and Dalmatian toadflax -- have made dramatic increases in the last 20 years, Brewer said. Bull thistle and Dalmatian toadflax make up 90 percent of the invasive or noxious weeds that infest 187,500 acres in Arizona.


Weed growth on native plants leads to a decline in ecosystem diversity and health. The weeds also increase bare soil, reducing the quality of habitat for animals that require native plants for ground cover or food.


Riparian corridors like the Verde River have had increases in tamarisk, or salt cedar, which use more water than native plants. The situation is especially worrisome because of the drought plaguing the West, Brewer said.


The U.S. Fish and Wildlife Service has raised some opposition to eradicating tamarisk because the federally protected Southwestern willow flycatcher nests in the shrubby tree, which forms along streams, displacing native trees such as cottonwood and willow.


"We understand or have a vision that restoration of the native habitat is the way to go. But to do all of it at one time would leave the flycatcher twisting in the wind," said U.S. Fish and Wildlife spokesman Jeff Humphrey.


Not treating the tamarisk could potentially lead to the loss of entire native riparian ecosystems, according the plan. Its deep roots use a lot of water and dry up springs and creeks. The foliage of salt cedars can add salt deposits to the soil, inhibiting the growth of other species.


Forest officials in Arizona are trying to stop such weeds before they get out of control, like they have elsewhere, Brewer said.


Noxious and invasive weeds are so bad in Montana and Wyoming that aerial spraying is just about the only solution to combat the weeds. Farmers and ranchers are selling their land because they can't afford to get rid of them, Brewer said.


"We're not at that point," Brewer said.


The weeds, native to Europe and Asia, were introduced to North America around the 1850s. They became established because of land management practices, timber sales, grazing, wildfires, the drought, and because the weeds don't have enemies and are not palatable, Brewer said.


"Once they got a toehold, they just exploded," Brewer said.


Source: Associated Press


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