Mount Davidson’s Garlon Pesticide – Again

The other day, we walked on Mount Davidson. The view from the top was lovely, and in the middle of it was a pesticide sign.

It was difficult to read because the moisture had condensed under the plastic. But we pressed it down, and were able to discern that it warned they were using Garlon 4 Ultra (a Tier I pesticide, Most Hazardous) against oxalis. (That’s the little yellow flower also called Bermuda Buttercup, or referred to as clover. Kids like to nibble on it because it’s sour.)

Oxalis grows from little underground tubers, called bulbils. Garlon isn’t very effective against oxalis because it kills the plant on top, but not the bulbils, which then can resprout.  Oxalis doesn’t set seed in San Francisco, so there’s no point killing the top of the plant before it flowers, either. It just deprives bees and butterflies of their nectar.

From the website, (which based it on a detailed study by the Marin Municipal Water Department)

These are the main issues with Garlon, in brief:

  • 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.”
  •  It very probably alters soil biology. “Garlon 4 can inhibit growth in the mycorrhizal fungi…” ( soil funguses that help plant nutrition.)
  •  It’s particularly dangerous to aquatic creatures: fish (particularly salmon); invertebrates; and aquatic plants.
  •  Garlon can persist in dead vegetation for up to two years.

The DEIR has said that the SF NAP’s phasing out Garlon.

If they are, it’s not apparent on Mount Davidson.  And we also saw another sign, this time warning about the use of Polaris (imazapyr) on cotoneaster.

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3 Responses to Mount Davidson’s Garlon Pesticide – Again

  1. The Marin Municipal Water District risk assessment of Garlon also said that one study reported significant reduction in the reproductive success of birds in places sprayed with Garlon. The number of eggs in the birds’ nests that hatched was significantly reduced where Garlon is sprayed.

  2. Joel s hipper says:

    Time to cut out the damn pesticides in our parks. They’re natural areas.. Get it?

  3. Garlon is an herbicide. At one of the neighborhood’s meetings on constructing a plan for Sutro Heights, I was stopped from reading information on this herbicide from the Material Safety Data Sheet by the moderator who was a representative from UCSF. He thought the information was too inflammatory. I urge all to check the MSDS to get the info from an official source. Bring this info too any meetings with the Parks and Rec Dept. or the City Government. You can get it from the internet.

    Philip Snyder

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