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Siskiyou WMA

Formed in 1999
Chaired by Patrick Griffin, Siskiyou County Agricultural Commissioner
General contact person Patrick Griffin, 530-841-4033,
Marla Knight 530-468-1238,
Mapping contact person Paul McCanna, Siskiyou County
Meetings Twice per year at the Siskiyou County Department of Agriculture, Yreka

Outreach Summary


  • Reprinting and circulation of "Selected Noxious Weeds of Northeastern California" a reference book for weed identification


  • Annual County Fair booth
  • Biennial weed tour throughout county
  • Annual noxious weeds display at Mother's Day flower show
  • Powerpoint presentations to various interest groups as needed
  • Display booth at July 4th celebration in Mount Shasta City

Media coverage

Newspaper insert distributed through several papers in county and at other events.

Project Highlights

Knapweed mapping and treatment in western Siskiyou County

In order to prevent the spread of knapweed species downstream, where agricultural lands could be impacted, or upslope to forests and rangeland, Siskiyou WMA treated populations of three knapweed species, reducing their density. Spotted, squarrose, and diffuse knapweed were mapped adjacent to U.S. Forest Service lands in the western part of the county using GPS/GIS, then mechanically or chemically treated. The acres infested by squarrose knapweed have been reduced from 1,600 acres to 30 acres. This reduction in density will prevent spread by vehicles, cattle, and mining equipment, which are vectors in this area. Project partners include U.S. Forest Service and Siskiyou County Department of Agriculture.

Eastern Siskiyou County perrenial pepperweed control

Perrenial pepperweed was chemically treated in the Tule Lake and Lower Klamath Federal Wildlife Refuges, in the eastern part of Siskiyou County. Treatments began at the outlying portions of infestations and worked their way towards the center of the infestations. Follow-up treatments are ongoing. Project partners include Tule Lake Irrigation District, the wildlife refuges, private ranchers and farmers, and Klamath County, Oregon.

Scott and Klamath River leafy spurge biocontrol

Siskiyou WMA partnered with California Department of Food and Agriculture, U.S. Forest Service, and Siskiyou County Department of Agriculture to control leafy spurge on Federal land along 60 miles of the Scott and Klamath Rivers. Two species of flea beetles and a longhorn beetle were used as biocontrol agents and were released at many sites along the rivers.

Musk and Scotch thistle treatment

Chemical and mechanical treatments were initiated on a project area of approximately 30,000 acres of Musk and Scotch thistle. Because it is so large, this site was originally designated as a containment and biological control site. The site is predominantly infested with musk thistle, but Scotch thistle has been increasing significantly. Siskiyou County Department of Agriculture partnered with Trinity National Forest to initiate the project and significant progress has been made.

Organizations on WMA’s MOU

Bureau of Land Management, Redding Field Office
Bureau of Reclamation
Butte Valley Resource Conservation District
California Department of Fish and Game
California Department of Food and Agriculture
California Department of Forestry
California Department of Transportation (Caltrans)
Klamath National Forest
Natural Resources Conservation Service
Rocky Mountain Elk Foundation
Salmon River Restoration Council, Resource Management
Shasta Resource Conservation District
Shasta/Trinity National Forest
Siskiyou County Department of Agriculture
Siskiyou County Farm Bureau
Siskiyou Resource Conservation District
University of California, Cooperative Extension
U.S.Fish and Wildlife Service