Noxious Weeds

Noxious Weeds Known to Occur in the Challis Field Office

Undesireable Plants Known to Occur in the Challis Field Office

Noxious weeds are a major concern in the Challis Field Office and throughout Idaho. Because noxious weeds produce large volumes of seed and have few natural competitors, they pose a serious threat to the health of wildlife habitats, river systems and recreation areas, as well as to pastures and croplands. Once established, noxious weeds spread quickly and overtake desirable plant communities. At their current rate of spread (estimated at 14 percent per year), noxious weed populations in Idaho are expected to double in less than six years. An estimated 1,000 acres in the Challis area are infected with noxious weeds and about 800 acres are treated annually to destroy these dangerous invaders.

BLM’s Challis Field Office is working to identify and reduce weed infestations in central Idaho. The most commonly occurring noxious weeds in the Challis Field Office are knapweed and leafy spurge. The majority of the noxious weeds in the Challis Field Office are introduced plants from other parts of the world, particularly Eastern Europe or Eurasia. Introduced plants become noxious weeds because the naturally occurring diseases and/or insects that would normally keep them under control were not introduced with the plants.

Custer and Lemhi counties often partner with BLM to perform much of the noxious weed control in the Challis Field Office. Preferred control methods include the use of herbicides, mechanical control and biological control. Herbicide control is the most frequently used method. Leafy spurge, spotted knapweed, henbane, dyer’s woad, toadflax and several varieties of thistle are most often controlled using herbicides. Other weeds require alternative treatment such as mechanical methods or biological control. Mechanical control (manual pulling) can be used in sensitive areas near streams. Biological control is the use of naturally occurring insects or diseases to attack a specific noxious weed.

There are also 22 undesirable species in the Challis Field Office which present management issues. These species are not listed on the state noxious weeds list because they are too widespread to mandate treatment, are not a significant agricultural threat or are troublesome, but not noxious. The primary undesireable plant species of concern is Cheatgrass, which threatens many areas of the Great Basin.

You can help prevent the spread of noxious weeds by taking simple steps while exploring and enjoying public lands. Recreationists and other public land users should be able to identify noxious weeds, understand their danger and take actions to prevent their spread. Boaters should clean boats and trailers, while campers and hikers should check all clothes and camping gear for seeds and clean the undersides of their cars. If a noxious weed is spotted on public lands, it is important to pull the weed up by the roots, dispose of all parts in a plastic bag and report its location and description to the nearest BLM field office or Forest Service. By taking preventative action, Challis will be able to maintain healthy rivers and wildlife habitats for years to come.

Challis Field Office  |  1151 Blue Mountain Road |  Challis, ID 83226
208-879-6200  |  Fax: 208-879-6219 |  Office hours: 7:45am - 4:30pm, M-F