SF Natural Areas Program: Imazapyr, Glyphosate Pesticides at McLaren Park

It looks like the SF NAP is using a lot of Imazapyr since San Francisco’s Department of the Environment approved it earlier this year.

We’ve seen signs on Twin Peaks, in Glen Canyon, at Stern Grove. Now someone has sent us photos of notices in McLaren Park.

This is despite these facts about Imazapyr:

  • It doesn’t bio-degrade easily;
  • It is pushed out by the roots of some plants it’s used on, thus spreading it further than intended;
  • Its breakdown product is neurotoxic;
  • It’s banned in the European Union.

In other words, this product, once applied, will spread further than it was applied, will hang around, and when it does break down will become a chemical that is neurotoxic. (Our initial article on Imazapyr is here.) It’s too poisonous for the EU, but it’s okay for San Francisco.

Source: Wikimedia commons

This time, it’s being used against fennel (the nursery plant of the native Anise Swallowtail butterfly) and bindweed.

It’s being used, apparently, along with glyphosate. We hope they’re not being used together. In most cases, very little or no research exists about two pesticides being used together. They may have synergistic effects that either one used along doesn’t have.

Again, there’s some confusion about the completion date. This sign had one filled in, but it’s been scribbled out. The dates of application also appear to have been overwritten. This raises questions: Did they just recycle an old notice? And, did they spray or didn’t they?


Of course, the Bay Area has a lot of (unexamined) experience with Imazapyr. We’ve been spraying it in the Bay for years, as part of a vegetation control project that has harmed Clapper Rail habitat.

This project attempts to battle spartina alterniflora (smooth cordgrass), a marsh plant native to the East Coast but not, apparently, to the West Coast. It is grows denser than the West Coast species, and it also grows year-round, unlike the local variety. Thus, it provides great cover and nesting sites for the Clapper Rail, a marsh bird whose numbers have been falling. Nativists have blamed red foxes, also native to other parts of the US.

But as this article, Nativism is Shooting us in the Foot on the website Death of a Million Trees points out, red foxes are native to the East Coast, and there both they and the Clapper Rail (and the spartina!) thrive.

Pouring on the Imazapyr and destroying the spartina alterniflora have demonstrably destroyed habitat. It’s also left a legacy chemical to join all the others in the Bay. Is this really something we want to replicate in San Francisco’s “Natural Areas”?

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3 Responses to SF Natural Areas Program: Imazapyr, Glyphosate Pesticides at McLaren Park

  1. Pingback: Nativism is shooting us in the foot « Death of a Million Trees

  2. Pingback: SNRAMP, Pesticides, and Mt Davidson | Save Mount Sutro Forest

  3. Kat Reid says:

    You are exactly right. Doesn’t anyone see the utter irony in using an environmental toxin, like imazapyr and other chemcial herbicides/pesticides, to “help” the enviornment. How much these native programs “help” the enviornment is not even well established. As you say, many of these programs harm the environment, not just with the synthetic herbicides (most of which end up in our groundwater and drinking water), but also by interfering with nature’s evolutionary response to changing climates and urban development.

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