Three Poisons on Mt Davidson: Garlon, Aquamaster, Milestone Pesticides

Recently, someone sent the San Francisco Forest Alliance this Pesticide Notice. It’s for Mount Davidson, for the end of January/ early February 2012. We found it shocking. Why?

It plans on using three of the most toxic pesticides San Francisco permits on Mount Davidson: Garlon 4 Ultra (Triclopyr); Milestone VM (Aminopyralid) and Aquamaster (Glyphosate). In several years of reviewing pesticide use on Natural Areas, we have not seen anything like this.

Garlon 4 Ultra and Milestone VM are Tier I chemicals, rated as “Most Hazardous” by San Francisco’s Department of the Environment. Their use is “Most Limited: justify use at public hearing.” Aquamaster, which has the same active ingredient as Roundup, is Tier II, More hazardous. (We have never seen the Natural Areas Program – NAP – use Tier III, Least Hazardous chemicals.)

Until now, we have not seen a situation where NAP uses two Tier I and a Tier II chemical in the same location.


1)  Garlon 4 Ultra, according to the guidelines published by San Francisco’s Department of the Environment (SFDoE) can be used as follows: “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. HIGH PRIORITY TO FIND ALTERNATIVE”  (The capitals are in the original guidelines.)

  • Garlon “causes severe birth defects in rats at relatively low levels of exposure.” Baby rats were born with brains outside their skulls, or no eyelids. Exposed adult females rats also had more failed pregnancies.
  • Rat and dog studies showed damage to the kidneys, the liver, and the blood.
  • About 1-2% of Garlon falling on human skin is absorbed within a day. For rodents, its absorbed twelve times as fast. It’s unclear what happens to predators such as hawks that eat the affected rodents.
  • Dogs  may be particularly vulnerable; their kidneys may not be able to handle Garlon as well as rats or humans.  Dow Chemical objected when the Environmental Protection agency noted decreased red-dye excretion as an adverse effect, so now it’s just listed as an “effect.”

2)  Milestone VM, also a Tier I chemical, has this note in the SFDoE guidelines:  “For invasive species in natural areas where other alternatives are ineffective, especially for invasive legumes and composites such as yellow star thistle and purple star thistle. Listed as Tier I due to persistence but toxicity & potential exposure are very low.

It deserves that Tier I ranking. Dow had to withdraw it from the UK because it was poisoning the compost.

It seems that this chemical is so persistent that if it’s sprayed on plants, and animals eat those plants, it still doesn’t break down. They excrete the stuff in their droppings. If those are composted — it still doesn’t break down the chemical. So now the compost’s got weedkiller in it, and it doesn’t nourish the plants fertilized with the compost, it kills them.

The manufacturer sees this as  a benefit. “Because of its residual activity, control can last all season long, or into the season after application on certain weed species,” says the Dow AgroSciences FAQ sheet.

What it means on Mt Davidson is that the chemical will be there for years. And, incidentally, none of the targeted plants – oxalis, erhata grass or Cape Ivy – are the “invasive legumes” or the star or purple thistle mentioned in the SFDoE guidelines.

3)  Aquamaster is a Tier II chemical. Here the SFDoE has made a recent change to its guidelines allowing terrestial use.

“Terrestrial uses: Spot application of areas inaccessible or too dangerous for hand methods, right of ways, utility access, or fire prevention. Use for cracks in hardscape, decomposed granite and edging only as last resort. OK for rennovations (sic) but must put in place weed prevention measures.”  The NAP reached a “last resort” 38 times last year (i.e. 2011).

Glyphosate has been associated with pregnancy problems and birth defects. A 2005 article published in the journal of the National Institutes of Health noted that glyphosate was toxic to placental cells (and Roundup was even more so):

“… glyphosate is toxic to human placental JEG3 cells within 18 hrs with concentrations lower than those found with agricultural use, and this effect increases with concentration and time or in the presence of Roundup adjuvants.”

In addition, it’s an endocrine disruptor.  French scientists published an article in the journal Toxicology titled, “Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines.”

For more about these and other pesticides the NAP uses, see The Natural Areas Program’s Pesticides: Toxic and Toxic-er on the Save Sutro Forest website.