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San Luis Obispo County, California


SLO County's Weed Management Area

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Weed Management Area’s Website


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Prevention & Control

Invasive Weeds

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Noxious weeds can negatively impact both our local economy and our cherished natural resources. There are many non-native, invasive plants established within San Luis Obispo County, threatening some of our most recognizable natural landmarks. In the photos above, yellow starthistle, artichoke thistle, and purple starthistle can all be found in the hills surrounding the scenic Morros. If left unchecked, these thistle infestations will likely expand, reducing rangeland productivity for county ranchers, whose cattle avoid the spiny, unpalatable plants. In addition, these weeds degrade our critical wildlands by displacing desirable native vegetation and diminishing the habitat value for local fauna. 

WMA Purpose

"Invasive plants alone are estimated to cause more than $20 billion per year in economic damage….. In addition to damage to the economy, our nation is losing precious habitat for native plants and animals and suffering mounting natural resource productivity losses to the encroachment of invasive plants and animals" - Dr Jim Tate, Science Advisor to Secretary of the Interior Gail Norton, April 29, 2003.

Although the issue of noxious weeds has not raised the concern of the general public like other more high profile ecological problems, the damage caused by invasive plants is unmistakable and recognized by countless economic, political, and environmental interests. A long-standing concern for the agricultural industry, noxious weeds are now well understood to be a major environmental problem as well, as non-native plants are increasingly invading even our most pristine natural habitats.

In recognition of the enormous problems that these invasive weeds can cause, and the coordinated effort that is required to effectively control them, the San Luis Obispo County Weed Management Area (WMA) was formed. The purpose of the WMA is multi-faceted: we are working to identify and map our county’s worst weed pests, implement projects designed to prevent, eradicate, or manage these invasive plants, and educate our local residents about this issue. 

Please take a few minutes to browse our website and learn a bit more about the problems associated with these plant pests