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Yolo County Weed Management Area

Project Summary
Type Non-Native Invasive Species Management
Project Lead Tanya Meyer/ Gillies Robertson
Partner Yolo County Department of Agriculture; Cache Creek Conservancy

Project Overview

The Yolo County Weed Management Area (YCWMA) was formed in 1999 by a coordinated effort between federal, state, county, and city agencies, private industry, and landowners that were jointly concerned about the explosion of invasive plant species in Yolo County.  The YCWMA promotes and coordinates efforts toward the management and control of the County’s noxious weeds through education and cooperation with landowners, agencies, organizations, and the general public.  The group is led by the Yolo County Department of Agriculture and the Yolo County Resource Conservation District (Yolo RCD).  There are a dozen active partners in the program.

In 2007, the YCWMA received a grant from the California Department of Food and Agriculture for three two year weed project in Yolo County.  Project One’s goal is to eradicate woolly distaff thistle (Carthamus lanatus) from Yolo County.  There is a small population in the hills above Guinda that we have identified and have been coordinating our resources for the survey, treatment, and monitoring the only existing infestation of the CDFA “B” rated woolly distaff thistle currently in Yolo County.    Project Two is the eradication of Distaff Thistle, Purple Loosestrife, Ravenna Grass and Yellow Flag Iris on Lower Cache Creek.  The goal is to identify and eradicate infestations of woolly distaff thistle (Carthamus lanatus), purple loosestrife (Lythrum salicaria), Ravenna Grass (saccharum ravennae) and yellow flag iris (Iris pseudacorus) in our management area, and prevent their spread along the riparian corridor of lower Cache Creek.  This work is being done by the Cache Creek Conservancy.  Project Three is the Early Detection & Eradication of A & B Rated Weeds in Yolo County and the project goal is to stop the spread of A & limited distribution B rated weeds.  The Yolo County Weed Management Area will conduct an A and select B rated weed local eradication project, with an emphasis on small incipient populations of A and B rated weeds.  This work is being done by the Ag Department.

Project Description

Start date December 2008
End date August 2012
Type of Activity
  • Monitoring the population of woolly distaff thistle and other weeds
  • Treating these weeds with the appropriate herbicide under the supervision of the Ag Department
  • Holding annual educational WMA meetings with partners
  • Reprinting the YCWMA educational brochure

Working to eradicate WDT from Yolo County, controlling that and other riparian weeds along a section of Cache Creek and holding WMA meetings.


To control weed populations to protect agriculture and wild lands in Yolo County.


Site Name

Cache Creek and areas of Yolo County

Size (acres) Guinda: 1,000 acres; Cache Creek about 11 miles

Additional Information


Woolly distaff thistle is closely related to safflower, an important crop in Yolo County.  If seeds from the Guinda population got into Cache Creek, and thus into the irrigation water system, it would cost the safflower industry countless dollars to deal with this noxious weed in their crop.

The other riparian weed along Cache Creek must be prevented from entering the Delta system from the creek, especially Ravanna grass, as it is currently only found along Cache Creek and is not yet spread to the Delta.

A and B rated weeds are highly invasive and detrimental to agricultural drops as well as reducing habitat quality in wildlands. 

Location Map, Yolo County Weed Management Area, Yolo County, California.




Source: California Department of Food and Agriculture

Amount: $58,594.48