Ivy Eradication: A Comedy of Errors

When the concert meadow in San Francisco’s Stern Grove was renovated in 2005, at a cost of $15 million, we were surprised that ivy was planted as the ground cover because ivy grows rampant in Stern Grove, shrouding many of the trees.  But, hey!  Who are we to question the choices of horticultural professionals? 

Ivy planted in Stern Grove, 2005

Now ivy is being sprayed with herbicide–presumably with the intention of killing it–by San Francisco’s Natural Areas Program in other parks in San Francisco, so one wonders if the staff who plant it are aware of the future of the ivy they plant.  Seems like another case of man creating problems which he then must solve.  Perhaps full employment is the objective, rather than the creation of a beautiful garden.  But we digress.

Ivy climbing trees in Stern Grove

Combining pesticides

Many members of the public are of the opinion that all pesticide (herbicides, insecticides, etc.) applications are inappropriate in a park that has been designated as a “natural area.”  Last year, the public complained about the spraying of Garlon in the natural areas by the Natural Areas Program because it is classified by the city’s Integrated Pest Management (IPM) policy as “Most Hazardous.”  Consequently, the Natural Areas Program significantly reduced its use of Garlon in 2011. 

For the most part they have substituted a mixture of glyphosate and imazapyr for Garlon. Is this an improvement?  Maybe not.  Although glyphosate and imazapyr have a lower hazard rating of “More Hazardous,” the Natural Areas Program increased their pesticide applications in 2011 at least 20% compared to 2010.  But more importantly, little is known about the toxicity of imazapyr and nothing is known about the toxicity of combining glyphosate and imazapyr.(1)  Imazapyr was approved for use in California in 2005, so only the minimal tests required by law have been done on it.

The manufacturer’s labels for these herbicides suggest that combining them is not an approved use.  The label for Aquamaster (glyphosate) does not include imazapyr on the list of pesticides with which it can be safely combined.  And the Polaris (imazapyr) label says it should not be combined with another pesticide unless it is expressly recommended by the manufacturer of that pesticide.

The “Aquatic Pesticide Application Plan for the San Francisco Estuary Invasive Spartina Project” is cited by San Francisco’s IPM program as the evaluation upon which it based its decision to add imazapyr to the list of pesticides approved for use in San Francisco in 2010.   The evaluation explained why imazapyr is being combined with glyphosate by the non-native Spartina eradication project. 

Imazapyr is apparently slow acting.  It can take some months before it kills the plant on which it is sprayed.  Glyphosate, on the other hand, is fast acting.  The plant on which it is sprayed begins to yellow and die within a few weeks.  Glyphosate is therefore used by the Spartina eradication project to provide quicker feedback to those spraying the herbicide.  They know within a few weeks if they have sprayed in the right place.  They don’t have to wait for the next season to spray again if necessary. 

Pesticide Application Notice, Glen Canyon Park, December 2011

 However, glyphosate should be applied to perennial broadleaf plants during their reproductive stage of growth, when they are budding in the late spring and summer, according to the manufacturer.  In Glen Canyon Park, a mixture of glyphosate and imazapyr was sprayed on ivy in December 2011, clearly not the recommended time period for spraying.  A month later, there is no indication that the ivy was damaged by this spraying.  This suggests that there was no point in combining glyphosate and imazapyr in this application.  The public was exposed to the unnecessary risk of combining these herbicides, with no potential benefit of taking that risk.


Pesticides accumulate and persist in the soil

Was it appropriate for the city’s IPM program to use the evaluation of imazapyr for the Spartina project as the basis of their decision to approve its use by the Natural Areas Program?  We don’t think so.  The circumstances of the Spartina project are substantially different from those of its use by the Natural Areas Program.

Imazapyr is used to eradicate non-native Spartina in a tidal estuary.  For that reason the evaluation of its use assured the public that this herbicide would not accumulate in the environment because it would be flushed away from the ground by the tide twice each day. 

The evaluation also said that when imazapyr was used in a pond or stable water source, it persisted in the ground for a longer period of time.  In fact, that’s exactly how imazapyr is being used by the Natural Areas Program.  It has been used at Lake Merced and at Pine Lake, both stable water sources.  It is also being used in Glen Canyon Park, which is a watershed. 

We don’t assume that imazapyr is being used safely to eradicate Spartina.  However, even if it is, it does NOT follow that it is safe for use in watersheds that are not tidal, such as those being sprayed by the Natural Areas Program. 

Collateral damage of pesticides

Glyphosate is a non-selective herbicide.  That is, it kills any plant it is sprayed on at the right stage of its growth.  But imazapyr is far more insidious as a killer of plants because it is known to travel from the roots of the plant that has been sprayed to the roots of other plants.  For that reason, the manufacturer cautions the user NOT to spray near the roots of any plant you don’t want to kill.  For example, the manufacturer says explicitly that imazapyr should not be sprayed under trees, because that tree is likely to be killed, whether or not that was the intention. 

Pesticide Application Notice under willow trees in Glen Canyon Park, December 2011

Much of the ivy that was sprayed by the Natural Areas Program in Glen Park in December 2011 was sprayed under willow trees.  The willow trees are native, so it seems unlikely that they intended to kill them.

Resistance to pesticides

The Federal Drug Administration recently banned some use of antibiotics in domesticated animals because the bacteria antibiotics are intended to kill are developing resistance to the antibiotics.  This resistance is becoming increasingly dangerous to humans who are also the victims of those bacteria.  Antibiotics are being rendered useless by overuse on domesticated animals.  When humans need them, they won’t work because bacteria have developed a resistance to them.

Likewise, plants and animals are also capable of developing resistance to pesticides.  Glyphosate is the most heavily used herbicide in agriculture.  Recent research indicates that weeds are developing resistance to glyphosate

The manufacturer of imazapyr says explicitly that repeated use of this herbicide is likely to result in resistance to it over the long term:  “When herbicides with the same mode of action are used repeatedly over several years to control the same weed species in the same application site, naturally occurring resistant weed biotypes may survive…propagate and become dominant in that site.”   So, does it make sense to use imazapyr on a plant as persistent as ivy? 

The GGNRA reported spending $600,000 over 3 years trying to eradicate ivy from 127 sites.  They were successful in only 7 of the sites.(2)  Obviously eradicating ivy is not a one-shot deal.

If ivy must be eradicated, pesticides do not have to be used to do it.  The Audubon Canyon Ranch in Bolinas Lagoon reported “qualified” success using hand-pulling methods on 5 acres over 5 years “utilizing 2375 volunteer hours.”  Biannual monitoring of resprouts will be required for the foreseeable future.  It’s a big commitment, but at least it is safe. 

All risk, no reward

Congratulations to any reader with the patience to slog through this tedious list of apparently incompetent use of pesticides by San Francisco’s misnamed Natural Areas Program.  We reward your persistence with this summary:

  • Combining pesticides is risky business because the toxicity of such combinations has not been tested.  Therefore, when there is no benefit in doing so, these combinations should be avoided.
  • A pesticide that is appropriate for one purpose is not necessarily appropriate for another.  In this case, imazapyr may not accumulate and persist in a tidal estuary, but it is more likely to do so in a stable watershed.
  • The Natural Areas Program may be killing plants it does not intend to kill by using herbicides indiscriminately.
  • Herbicides should not be used repeatedly on the same plants in the same locations because the plants will develop resistance to those herbicides. 
  • If the Recreation and Park Department is planting ivy in one park and destroying it another, could it be such a bad plant that it is worthwhile to expose the public to toxic pesticides?  We don’t think so, but if we are wrong, then ivy should be removed by hand without using pesticides.

(1) “Aquatic Pesticide Application Plan for the San Francisco Estuary Invasive Spartina Project,” August 2010, page 32.

(2) Liston, Heather, “Reuniting old adversaries can beat back exotic invaders,” California Wild, Winter 2006

13 thoughts on “Ivy Eradication: A Comedy of Errors”

  1. It’s very suspicious that these people plant things that later need eradication…can you say “make work project”? or “public ripoff”?

    Webmaster: We’re inclined to think it is more an example of the right-hand not knowing what the left-hand is doing. One branch of the Rec & Park Dept is planting ivy while another branch (the Natural Areas Program) is killing it.

    Also, ever notice that the chain of “invasive” plants leads to Monsanto and Dow? They always pick plants that require these products to attack…even though there is no real eradication, just the promise of it. Another taxpayer ripoff.

    Webmaster: Yes, we’ve noticed this, but we doubt the connection is direct. The advertising and public relations efforts of these chemical companies certainly support nativism. However, the use of these toxic chemicals seems primarily a reflection of ignorance of their toxicity and the deep commitment to native plants which trumps all other considerations.

  2. …”Combining pesticides is risky business because the toxicity of such combinations has not been tested. Therefore, when there is no benefit in doing so, these combinations should be avoided.”

    I beg to differ with Million Trees. It seems to me that these combinations should be avoided in EVERY situation until their safety has been established by thorough testing.

    Webmaster: Yes, that would be safer.

  3. I live on the coast in Wa. state and they have classified Japanese eel grass as a class “c” weed . This allows for the spraying of these same chemicals on commercial shellfish beds to control this grass along with spartina. They are also testing a new chemical” imadicloprid” to replace carbaryl for mud shrimp control.(used since 1964 and outlawed in 2012) Please do a story on the dangers of eating these chemical filtering oysters and clams . Thank you for all you do…

  4. FYI– My letter to the Editor: I live on the coast in Wa. state where they have recently classified Japanese eel grass as a class “c” weed . This will allow for even more spraying of the chemicals “imazapyr” and “glyphosate” (ROUNDUP) on commercial shellfish beds to control this grass along with spartina grass. (allowed on spartina since 1996). They are also testing a new chemical” imadicloprid” to replace carbaryl (SEVIN) for mud shrimp control on these same beds.(SEVIN was used since 1964 and outlawed in 2012)
    Please tell all your family and friends of the potential dangers of eating these chemical filtering oysters and clams . SEVIN was outlawed after 48 years .( probably after they figured out the long term effects). Don’t be their new guinea pigs for their next new and improved poison. Before ordering or buying, ask if they spray!..

    1. Imidacloprid is an insecticide, in the family of new chlorinated synthetic poisons called neonicotinoids. These are a category of highly water soluble poisons that combine the water solubility of a chlorinated compound with the age-old toxicity of the naturally occurring and poorly soluble nicotine alkaloids (tobacco). These poisons are indicted as a primary cause of colony collapse disorder, CCD, the die-off of honeybees and other pollinators that is occurring.

      While many countries in Europe have banned or restricted Imidacloprid and other ‘neo-nicotonyl’ poisons, the US deregulated them. They are for sale everywhere, and “soil drenching” to make the whole plant toxic is the new gardener’s advice for any bug that bothers them. They are a systemic poison, so you can’t wash the poison off the foods, such as beets, tomatoes, corn, and other grains that are treated with them. They are very toxic to aquatic invertebrates, earthworms, lady bugs, lacewings… and bird and fish population are crashing as result of the widespread use.

      In my part of the country, the southern end of the Appalachians, the public forests are under assault with Imidacloprid (Bayer’s Merit) and dinotefuran (Safari). New York State never allowed Safari due to it’s extreme toxicity. Invasive bugs are the reason for poisoning the soil and therefore the waters of the region, while making a few chosen trees too toxic for insects to eat on them.

      These chemicals are neurotoxins, and while Bayer would have us believe that the nerve connections of insects are different from animals, many animals are affected by these poisons. Any exposure causes irreversible damage to nerve pathways–that’s the method of lethal action. Read more at disasterinthemaking.com or the Xerxes Society reports on Imidacloprid or farmlandbirds.net. Let the EPA know that you want these banned. NRDC and Sierra have long called for their ban, and the EPA has a public comment open on clothianidin now (9/12).

      Tell others that even the pollen from today’s grain crops is toxic to bees, birds, and aquatic life. Why is this being used all over the forests?–‘pest’ insects, such as hemlock wooly adelgid and emerald ash borer shouldn’t be an excuse to wipe out insects birds, and fishes indiscriminately.

      And don’t support ‘forest groups’ that do support using these poisons. Unfortunately groups as diverse as Arbor Day Foundation, Audubon Society, Appalachian Trail Club, Wilderness Society and many local groups think using these poisons is the solution to…just what, exactly, nature changing?

  5. Thanks to Death of a Million Trees for all you do. If I have to choose between mother nature and Monsanto, Dow,BASF, Bayer and Nufarm, I have no choice but to choose mother nature. Once man has changed the environment by planting something or other, mother nature takes over and I think she knows best from the perspective of our planet, perhaps not from the perspective of homo sapiens.

  6. I am afraid that few gardeners can resist the convenience of
    “Roundup” and according to “Audubon Canyon Ranch”
    personnel they use it “when necessary”.
    Webmaster: Using pesticides in your own backyard is one thing. Using them in a public park is another matter. In your own backyard, you’re free to do almost anything you wish, including poison yourself. In the public’s backyard, doesn’t the public have something to say about it? We think they should.

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