The Mendocino National Forest is proposing to spray herbicides across 54 acres to kill brooms—Scotch, Spanish, and French brooms—highly-invasive species that outcompete natives, form dense thickets, and provide little sustenance to native wildlife. The project is in response to the 2018 Ranch Fire, which burned large swaths of the national forest, including the areas proposed for treatment. The existing broom was incinerated in the fire and returning vegetation, either from regenerating root structures unaffected by the fire or from seed left in the soil. The Forest Service now proposes to spray these young and emerging brooms, arguing that the herbicide application, together with the synergistic effects from the fire, can fully kill off broom—a “kick-‘em-while-they’re-down” approach to weed management.
Here, the proposed herbicide application would be a mixture of triclopyr and aminopyralid, along with a seed oil surfactant and a marker dye. Triclopyr is of low to moderate acute toxicity in mammals, and long-term exposure has been found to result in kidney and liver effects. It is believed to be toxic in fish species and is “mobile,” dislodging from soil particles and joining water. Aminopyralid is in the same family of pesticides as triclopyr. It is a relatively new pesticide and, thus, there is little information about its relative toxicity. It is not believed to be cancer forming and is thought to be non-toxic to wildlife and does not appear to bioaccumulate. The proposed plan contains some measures to reduce risk associated with spraying. According to the Forest Service, “All components would be applied at or below the label rates, and the mixture applied with backpack sprayers. No herbicide will be applied within Snow Mountain Wilderness, and no aerial application of herbicide is proposed.”
The use of herbicides to control invasive species is controversial. The case for herbicide usage goes like this: herbicides are a cheap way to kill invasives and enable cash-strapped groups to treat larger areas than could be accomplished with manual removal. And if applied effectively, with adequate follow-up treatments, herbicide use can effectively remove invasives and allow for native plants to regenerate. In many cases, however, invasive species are a futile effort because the applicator applies it as a one-and-done effort, failing to come back for follow-up treatments. For broom species, whose seeds can lay dormant for up to 50 years, these return treatments are often necessary. Herbicides also carry with them risks, both to human health and the natural environment. Careful application can reduce that risk but not fully eliminate it. For that reason, EPIC generally promotes manual removal of invasive species when possible.
The proposed herbicide application is in “scoping,” meaning that the environmental analysis for this project is just beginning. At the heart of EPIC’s scoping comments are a desire for the Forest Service to consider increasing manual removal, particularly around waterbodies. Part of the planned operations are nearby Lake Pillsbury. Given the solubility of triclopyr and its toxicity to fish, particularly rainbow trout, this appears to be the highest-risk area for spraying. For a similar project on the Shasta-Trinity National Forest, EPIC worked with the Forest Service to treat riparian areas by hand, and even led work parties to pull Scotch broom .
For more on this project, please consult the Forest Service’s website at https://www.fs.usda.gov/project/?project=57273