San Francisco Herbicides 2015: Why Better Isn’t Good Enough

SF Natural Areas Pesticide by Active Ingredient 2008-2015 sm

NAP’s pesticide usage is down again in 2015

We have some nearly good news. After years of increasing pesticide until 2014, the 2015 data shows Natural Areas Program (NAP) again used less herbicides than in the year before – though they applied it more often. The volume of herbicide used was the smallest amount since 2010, but the number of applications the highest since 2008 (the earliest data we have).

So why isn’t this good enough?

  • The main reason is the growing consensus that herbicides are more toxic than the manufacturers claim. Roundup (glyphosate), long regarded as a “safe” pesticide (though not by us – we wrote about the worrisome scientific data HERE and HERE) has been declared a probable carcinogen. Herbicides don’t have a place in our parks where they could impact people – especially those who have reasons to worry about their toxic load – children, who are more sensitive because of their size and fast growth, and pets. People just don’t want any herbicides in our parks, especially in “Natural Areas.”
  • SF Natural Areas Program Number of pesticide applicns 2008-2015 sm

    But the number of applications is up.

    The second is that though NAP has reduced the amount of herbicides they use, they have considerably increased the number of applications. This means that park-goers have a higher probability of encountering pesticide use.

  • Some of these pesticides remain in the soil and environment for months, even years, after application. Imazapyr’s breakdown product is a neurotoxin. Many of the Natural Areas are on high ground, or in watersheds, and poisons applied there can spread unpredictably.
  • NAP used a dispropotionately large amount of the most toxic herbicides compared with all of SF Recreation and Parks Department (SFRPD):
    • 35% of the Roundup (glyphosate);
    • 80% of the Garlon (triclopyr) and
    • nearly 100% of the Stalker (imazapyr) and Milestone (aminopyralid).


A case in point is Garlon (triclopyr). This is one of the most toxic herbicides permitted on city-owned properties, with a Tier I (Most Hazardous) rating.

Photo credit: Badjonni (Creative Commons - Flickr)

Photo credit: Badjonni (Creative Commons – Flickr)

NAP is the most regular user of Garlon, mainly to poison yellow oxalis.  In 2015, it accounted for 80% of the Garlon used by SFRPD.They are trying to reduce usage with a new surfactant (the stuff used to dilute the herbicide and let it spread better), CMR Silicone Surfactant. We are unsure whether this is an improvement but will research it further. The Label is here: Cmr_Silicone_Surfactant_(0198050402)_Label

If NAP stopped trying to poison oxalis each spring, Garlon could be removed from the approved list of pesticides. Instead, they used Garlon five times in December, on Twin Peaks, Glen Canyon, Mount Davidson, and McLaren Park. These are places where children and pets could easily encounter the herbicide.

coyote pouncing in oxalis field - copyright Janet Kessler

There’s no need to battle oxalis. It’s beloved by children, attractive to bees and butterflies, useful to other wildlife in the food chain, and a valuable plant that improves the soil for grasses. Moreover, it disappears after its flowering period is over. There is no evidence that it adversely affects other plants in what is essentially a non-native grassland.


Roundup is the most commonly used pesticide in our parks, and NAP uses a disproportionate amount. It applied Roundup over 70 times in 2015, and the volume used was more than in 2014. We would have expected that after the World Health Organization finding, NAP would stop using this herbicide. It appears not.

The problem is that NAP targets a lot of plant species it considers invasive – at the last count, around three dozen different species. Unless it changes its objectives, it will always need herbicides – Roundup, Stalker/ Polaris, Milestone VM, Garlon 4 Ultra. If it reduces one, there’s a temptation to increase another.


San Francisco can get rid of herbicides in natural areas. It will mean a change in the mindset of land managers. Non-native plants are valuable in wild places for their ecological benefits – carbon capture, wildlife habitat and food, soil enrichment and erosion prevention among others. If we must create native plant gardens, they should be small enough that they can be managed by manual gardening. Though we have issues with what UCSF is doing in Sutro Forest, in one matter they have a clear win: No pesticides have been used there since 2008, and UCSF have committed not to use any herbicides in Sutro Forest. That includes the native plant garden on the summit.


SFRPD Pesticides (ex Harding and NAP) 2013-15SFRPD reduced its herbicide usage in 2015 as well. The numbers for 2014 were exceptionally high because of large amounts of Tier I pesticides used in the Kezar Stadium renovation, and mistakenly in Gleneagles Golf Course. Without those two factors, usage would have declined in 2014 and been nearly flat in 2015.

A word about Greenmatch and Avenger. These are based on lemongrass oil, or what is called a “botanical.” It’s actually considered acceptable for organic gardening. However, it’s classified as Tier II because it can cause allergic reactions in its undiluted form.


The renovation of Kezar Stadium has used a lot of Tier I herbicide.

  • In November and December 2014, they used 208 fluid ounces of Drive XLR8 for turf renovation. This was a one-off Tier I pesticide use, and may have been associated with bird deaths in the area.
  • In February 2015, they used 320 fluid ounces of Fiesta, also classified as Tier I, followed by 24 ounces of Aquamaster (which was subsequently classified as Tier I).
  • In June 2015, they used 16 ounces of Turflon (triclopyr), also Tier I and one of the few times any SFRPD department but NAP used triclopyr.

They have also used some Tier III herbicides – actinovate and fosphite – which we presume are a lot less toxic. (Edited to Add: They are not included in the graph above for that reason.)

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