CalTrans Using Glyphosate on Sonoma County highways

Cal Trans douses Sonoma County with a “probable” cancer causing ingredient, RoundUp or glyphosate. 

Let your representatives know this is not acceptable. Why have they resorted to toxin spraying when mowing has been ongoing for years. Our pollinators are declining rapidly due to practices just like this…..


Here is how they responded to inquiries:

What kind and how much herbicide has been sprayed?

Caltrans sprays glyphosate, the active ingredient in Roundup. We use the amount prescribed by the makers of the product.

Integrated Vegetation Management:


Glyphosate usage in Sonoma County on vineyards per California Dept. of Pesticide Regulations.

To control roadside vegetation, Caltrans implements a program called Integrated Vegetation Management (IVM), a practice using several methods of vegetation control, including herbicides, mowing, and weed trimming. Over the past several years, we have markedly reduced our use of herbicides.


Good vegetation control is needed for the safety of motorists and cyclists. Tall weeds obscure traffic signs and block sightlines, making it difficult for drivers to see around bends in the road. Fire danger is another concern. Dry weeds make natural fuel for wildfires, which, as we know, have devastated large swaths of California in the past few years. An invasive plant called stinkwort is thriving along the highways where it competes with local vegetation.


Caltrans typically sprays herbicides in areas where the safety of Caltrans workers might be jeopardized by fast-moving traffic or lack of visibility. In locations where stinkwort thrives, herbicide is used because of the plant’s tenacity, and because mowing or weed trimming exacerbates the problem by spreading the seeds.


Caltrans workers are trained to follow federal and state laws regarding pesticide use. All herbicides are used according to their federal label, California Code of Regulations, and Caltrans policy. The herbicides Caltrans uses are registered with the Environmental Protection Agency and the California Department of Pesticide Regulation. Caltrans reviews its list and approves the use of the herbicides, which include glyphosate.

When applying herbicides, Caltrans follows strict protocols, including leaving buffer zones adjacent to creeks, wetlands, waterways and drainage outlets. Likewise, Caltrans maintain buffer zones around private driveways and mailboxes. Caltrans reviews its policies of herbicide application every year to keep current with best policies of managing vegetation along state highways.

I hope this letter has answered the questions which you have regarding the use of herbicides in Sonoma County.

Jeff Weiss

Caltrans Public Information

(510) 286-5543