Siskiyou County Weed Management Area

WMAs are local stakeholder groups working on weed projects. Typically, they are organized by county, through county Agricultural Commissioners' offices. All interested land management entities, public and private, are invited to participate. Official WMA partners sign a Memorandum of Understanding indicating their commitment to working on invasive plant problems to the extent resources allow. Each WMA develops a strategic plan that identifies their top priorities for local management. Together these partners plan and implement projects on-the-ground, and collaborate on mapping and public education. 

California's WMAs have proven to be an efficient and effective instrument for controlling the spread and impact of invasive weeds throughout the state. The program has grown to include (from CDFA program report) 48 WMAs covering all 58 counties. Because they are local efforts that involve all land management stakeholders, their work has strong local support.

Siskiyou County WMA

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


  • 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.


Contact Siskiyou County Weed Management Area

Patrick Griffin
Siskiyou County Agricultural Commissioner
525 South Foothill Dr.
Yreka, California  96097
Phone: 530-841-4033
Fax: 530-842-6690


Service Area

Services provided in:
  • Siskiyou County, California

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