Garlon in our Reservoir?

Someone sent us this picture, taken on 20th Jan 2011 at Twin Peaks. We were surprised, even though we’ve grown accustomed to seeing notices of toxic pesticides being used all over “Natural Areas.”


Garlon [ETA: i.e., triclopyr] is a very toxic herbicide. San Francisco’s Department of the Environment (DOE) classifies it as Tier I: Most Hazardous. It’s listed as HIGH PRIORITY TO FIND AN ALTERNATIVE (their caps).  The use restrictions say: “Use only for targeted treatments of high profile or highly invasive exotics via dabbing or injection. May use for targeted spraying only when dabbing or injection are not feasible, and only with use of a respirator.”

So what was so surprising about this one? Well, several things.

1.  Its location.

Here’s a picture of the sign in context. It’s just across a trail from the Twin Peaks reservoir — used for fire-fighting, but also as back-up city water supply in case of an emergency.

Garlon and Aquamaster near Twin Peaks Reservoir

2. Mistake in the notice.

The date is missing from the notice. There’s no way to tell when the spraying was or will be done.  It’ll be some morning before 1 p.m.  Unless you see them up there spraying (and we recommend not) how would you know when to avoid the place?

3.  The broad range of plants targeted.

Cotoneaster. Eucalyptus. French Broom. Pampas. That’s the most we’ve spotted so far. In other notices, Garlon’s been used on erhata grass.  Picris and Poison Oak. “Invasive weeds.” Pittosporum. “Woody weeds and stump treatments” (in an area where we saw nothing woody) and oxalis. This appears to cover any non-native plant on “Natural Areas.”

Some of those earlier notices were actually for Garlon 4 Ultra, which was not supposed to be sprayed. (The January 2011 pesticides list asks for an exception for “targeted micro spraying” of that chemical.) We’re not sure how they were dabbing it on oxalis…

4.  Early in the Year

We’d assumed spraying would start in late February or March. Late January took us by surprise. Is there any month in which there’s no pesticides on Twin Peaks?


Aquamaster (which has the same active ingredient as Roundup, glyphosate)  is a Tier II pesticide in San Francisco.  Its use is subject to limitations slightly less stringent than those on Garlon. What the 2011 Reduced Risk Pesticide Use list says about Aquamaster is: “May damage non-target plants. Use for emergent plants in ponds, lakes, drainage canals, and areas around water or within watershed areas. Only as a last resort when other management practices are ineffective….Note prohibition on use within buffer zone (generally 60 feet) around water bodies in red-legged frog habitat.

The research on the effects of each of these chemicals is incomplete, and more concerning data continue to emerge — such as the effect of glyphosate on birth defects.

In combination, synergies could exist, making them more toxic or more persistent than either pesticide alone. We haven’t been able to find any research on these effects; Chris Geiger of the Department of the Environment said it would be difficult because the chemicals companies don’t reveal their “inert” ingredients.


SF’s DOE regulates pesticide use on City property. We attended a recent meeting to discuss changes to the list for the coming year ahead. Here are the citizen suggestions we sent to Dept of Environment and Rec & Parks:

1. No combination use of pesticides, except for emergency or public health reasons.

In discussion, Chris Geiger of the DOE pointed out, not only are synergistic effects unknown, they may at this point be unknowable because companies do not reveal “inert” components — which might not actually be so inert. Garlon and glyphosate are used in combination in a number of Natural Area Program areas. Many of these are watersheds.

[Edited to Add:  In March 2011, Lisa Wayne, Natural Areas Manager, confirmed they won’t be doing it any more. “The Natural Areas Program will not be combining Garlon and Roundup in simultaneous spraying in the future.”]

2. No use of any Tier I or II herbicide in Natural Areas.

I understand the desire to control weeds and restore Native Plants, but the trade-off here seems excessive. In particular, areas that are watershed, high ground above neighborhoods, and waterbodies should not be contaminated with high-risk or high-persistence herbicides. It’s ironic that Sharp Park Golf Course uses *no* herbicides, according to a report from Rec & Parks’ Ralph Montana [ETA: Since Aug 2010, when Roundup was used there once], while the “Natural” areas regularly use Garlon.

3. In reclassifying Roundup, the latest studies — and evidence of attempts to suppress them — should be taken into account.

It’s not just the surfactant. It’s the glyphosate. We’ve posted about it here.

4. Better record-keeping, and more attention to conforming to rules and guidelines, particularly in Natural Areas.

This Program seems to have had multiple violations in the last couple of years. We understand the effect of tight staffing, but without accurate record-keeping and rules actually being followed, DOE oversight becomes moot. The record should show which area is being sprayed and specifically what pest is being targeted.

Lisa Wayne of SF’s Natural Areas Program responded to these suggestions:

“The Natural Areas Program is committed to implementing least toxic methods of weed control that are feasible and allow us to fulfill our mandate of preserving and enhancing biodiversity in the City.  This is not always an easy balance to achieve and our approaches are constantly evolving.   The Natural Areas Program works with thousands of volunteers each year (10,000 to 15,000 volunteer hours) performing hand removal of invasive plants; however, some species cannot be feasibly removed by hand and require herbicide treatment.

“In addition, we are constantly investigating least toxic herbicide alternatives.  For example, we are in the process of phasing out Garlon; however, we have yet to find a product that can be used for broadleaf plants like oxalis in grasslands that do not impact monocots (bulbs and grasses) that we are trying to protect.  We will continue to work with the Department of the Environment and the RPD Integrated Pest Management toward this effort.   I will speak to Chris Geiger further about your concerns related to mixing of chemical; however, I know this to be a common practice in park management.”


At present, UCSF uses no herbicides at all in Sutro Forest. This could change as early as September 2011, when it will  start felling trees and mowing down the undergrowth and using toxic chemicals to prevent their regrowth.

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6 Responses to Garlon in our Reservoir?

  1. Pingback: It’s Spring! It’s Twin Peaks! It’s toxic Garlon herbicide! | Save Mount Sutro Forest

  2. jim says:

    Garlon 4 is “Triclopyr” not “Glycophosphate”. Garlon actually breaks down faster than Glyco in the environment. We’ve used hundreds of gallons of this stuff at our Ranch this year to kill poison oak. There aren’t many alternatives

    • webmaster says:

      Hi Jim, thanks for writing. Yes of course Garlon 4 is Triclopyr, not glyphosate. We’ve written about it here:
      In this case, they were using both glyphosate and triclopyr.

      Apparently, triclopyr can persist for up to two years in dead vegetation. It’s sad that there are no alternatives on your Ranch. Please do take care: It’s pretty toxic stuff, rated a “Tier I” chemical by San Francisco city. It’s not what we want for our natural areas, especially on high ground.

  3. Pingback: Twin Peaks: Sunset and Evening Fog and Pesticides | Save Mount Sutro Forest

  4. Pingback: San Francisco Natural Areas and Escalating Pesticide Use | Save Mount Sutro Forest

  5. Pingback: Escalating pesticide use by the unnatural Natural Areas Program « Death of a Million Trees

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