Lifelong arborist Tom Kent for months has suspected that an herbicide was sprayed on a douglas fir stump in Inverness Park. The faded grey-and-red circle ringing the stump was not a natural feature, he surmised, but instead the dye from an herbicide spray likely applied by a tree-service company.
His suspicion turned out to be correct.
According to records filed with the county, Davey Tree Company, which contracts with Pacific Gas & Electric to rid West Marin roadways of trees at risk of downing power lines, has been applying Garlon 4 Ultra to severed stumps since 2013. Applying the herbicide to keep trees from re-sprouting is a vegetation-control practice that falls within P.G.&E.’s Public Safety and Reliability Project, which started in 2007.
In August, PG&E will begin inspecting West Marin to identify electrical circuits most prone to vegetation-caused outages and tally trees for the chopping block. In the fall, those trees will be cut down; Garlon 4 Ultra will be applied where property owners give permission, according to P.G.&E. spokesman Joe Molica.
“We only apply herbicide to cut trees and in the minimum amount,” Mr. Molica said. “It’s on a case-by-case basis, only if needed and only if the property owner agrees to it.”
But Christine DeCamp, who rents the property where Mr. Kent identified the treated stump, said she was not informed beforehand that the tree would be cut down or an herbicide applied. Rather, a couple of months ago, she approached the tree crew that was working to remove the fir, which jutted out from an embankment on the bay side of Sir Francis Drake Boulevard.
Ms. DeCamp said she emailed her landlord, who gave little information on why the tree was being cut and said nothing about herbicides. She remembered that soon after the tree was cut, a bright green ring was present around the stump’s circumference. That ring, she said, washed away with rainfall.
“If you’re not around when they come, you don’t get an option,” said Ms. DeCamp, who has lived in Inverness Park for 24 years. “They just do it.”
Garlon-brand herbicides are commonly used for controlling vegetation throughout the county, according to Stefan Parnay, the deputy commissioner of the county’s department of Agriculture, Weights and Measures. Tree-service companies are required to submit monthly reports that list which herbicides they used and in what quantities.
Though Mr. Molica told the Light that P.G.&E.’s applications abide by federal, state and local laws, some residents are not pleased by the presence of herbicides in their backyard. “There is no such thing as an herbicide that’s benign,” Mr. Kent said. “Why not just come back and trim [the tree] when it grows back?”
Triclopyr, the active ingredient in Garlon 4 Ultra, is a broadleaf herbicide used most often on pastures, woodlands and rights-of-way. It meets the California Department of Pesticide Regulation’s criteria for a potential groundwater contaminant and, according to the Environmental Protection Agency, has proved toxic to many fish species, including coho salmon.
Few studies have been done that assess the risk of triclopyr to humans, and most of the toxicity data that has been gathered on it was ascertained through laboratory tests on animals. No studies have been done specifically on Garlon 4 Ultra, according to a 2010 risk assessment of triclopyr completed by the Marin Municipal Water District.
Triclopyr keeps trees from re-sprouting by mimicking plant growth hormones, called auxins, to first elongate broadleaf plants, then to distort, wither and kill them. Grasses that surround broadleaf plants treated with triclopyr are not affected because they can quickly transform the herbicide into compounds that do not have hormonal activity, according to the Journal of Pesticide Reform.
Paul Reffell, a longtime environmental activist in West Marin, cautioned that studies are rarely done on the entire formulation of an herbicide, which includes both “active” and “inert” ingredients. Often, he said, an herbicide’s inert ingredients may be as harmful—or even more harmful—than the active ingredients.
“One troubling aspect is the use of pesticides like this around bodies of water in our watersheds,” Mr. Reffell said. “Given the right conditions, these toxins can leach through soil and into the bay and creeks.”
Chanty Mou, a supervisor for Davey Tree, said his crew does not apply the herbicide on stumps close to waterways.
The Pesticide Action Network North America, which advocates for pesticide alternatives, notes that triclopyr is slightly toxic to honeybees. “In general, blanket use of herbicides can do more harm than good, and shouldn’t be a substitute for sustainable weed management,” said Paul Towers, the organization’s spokesperson.
In the coming months, P.G.&E. will be making phone calls and sending letters to communicate with customers about the upcoming Public Safety and Reliability Project. The company will “primarily be contacting customers who have trees, or parts of trees, that are at risk of falling onto a power line,” Mr. Molica said.
For now, trees bearing spray-painted dots and x’s that mark them for future trimming or removal line roads like Drake’s View Drive. There, large sections of mature tree trunks—often several feet long—lay strewn in ivy-infested embankments. Though Mr. Molica said the companies leave these sections for nearby homeowners to use however they please, it’s a sight that irks Mr. Kent, who has called the abandoned wood sections “a mess.”
Aside from being more open about the use of herbicides, he wishes that P.G.&E. and its contracted companies would clean up more thoroughly after finishing the tree-clearance work. “They leave the wood all helter-skelter,” Mr. Kent said. “As long as they can say it’s not unsafe, they do not care about how it looks. You’re just leaving a big job in everyone’s lap.”