Greensboro and other communities debate herbicide use on invasives.

By Lorry Martinez, for the Community News Service

GREENSBORO — Across Vermont, invasive species are crowding out native plants, leading to soil erosion, habitat loss for pollinators, and reduced biodiversity.

To get rid of invasives, the most effective methods are a combination of mechanical removal and careful use of herbicides, such as glyphosate, according to many experts.

However, the use of glyphosate worries some conservationists.

“I would categorize it as disgracefully understudied when you consider the amount of these chemicals that’s being applied on our landscape,” said Mike Tiernan, co-founder of Bee The Change, a Weybridge-based group that plants native species for pollinator habitat. Tiernan also works as an emergency room physician at Porter Hospital in Middlebury.

Without herbicides, the alternative option is physically removing invasives.

There’s a lot of energy for mechanical removal in the beginning, but enthusiasm can fade after the first couple of years, says Will Marlier, Lake Watershed Program Specialist for the Orleans County Natural Resource Conservation District. 

“Sometimes herbicide is necessary where mechanical options aren’t really on the table,” Marlier said. “It should be limited, it should be used cautiously, it should follow state regulations, and it should be done ideally by a licensed herbicide applicator.”

This issue recently came to a head in Greensboro. After some debate, the Greensboro Conservation Commission (GCC) was granted $3,000 at Town Meeting in March.

GCC intends to use some of these funds for testing herbicide as a knotweed control method at a pilot site, Highland Lodge. 

Concerns over whether glyphosate use is in conflict with Greensboro’s Pollinator Resolution have also been raised. It urges residents to commit to “avoiding use of insecticides, including systemic insecticides on their property wherever possible”. 

Smith’s Grocery, which was initially another pilot site, declined chemical treatment due to customer concerns. They have expressed openness to mechanical hand-pulling of knotweed instead. 

Japanese knotweed (Reynoutria japonica) is a non-native shrub that aggressively replaces native plants once established. There’s widespread agreement about the need to address the problem.

Still, the use of glyphosate to control knotweed has caused much debate over its safety and efficacy. The Environmental Protection Agency (EPA) has concluded that glyphosate is not likely to cause cancer in humans, but the International Agency for Research on Cancer (IARC) has classified glyphosate as “probably carcinogenic.” 

Pollinator Friendly Greensboro, a local advocacy group that has worked with Bee The Change, has raised concerns about herbicides’ potential to affect organisms outside its target, especially pollinating insects. 

In his own experience with ecosystem restoration, Tiernan recommends practices like cover cropping and mowing, depending on the invasive plant he’s dealing with.

Tiernan explains that many pesticides use a systemic approach, where the chemical spreads from the application site throughout the rest of the plant. This can potentially affect the pollen and nectar that feeds pollinators.

“It’s got this fallacy that we could put [herbicides] on the land and it doesn’t end up inside of us,” Tiernan said.

Non-chemical options often require a large, consistent volunteer efforts for several years, but do so without bringing in potential side effects from chemicals.

Chemical options are typically more effective and have shorter timelines, but require careful research and adherence to safety guidelines, Marlier said. In addition to his professional role, he is a member of the GCC.

“Where the volunteer capacity exists on sites where the access is reasonably accessible, mechanical treatment is probably my preference,” Marlier said.

“But the requirement for long-term volunteer efforts spanning, you know, a decade is really hard to maintain. And it’s rare that a community does that successfully,” he said.

Lars Lund, a Protection Forester for Vermont’s Agency of Natural Resources, said herbicide labels contain detailed information on intended concentration, amount, and method of delivery.

“If they’re very careful about how they apply it and they just get it on the plant itself, then there shouldn’t be any issues with pollination,” Lund said.

“I know that there’s the flowers on the plant, potentially bees would come and want to pollinate that; you could time it for when they’re not in flower,” Lund said.. 

Marlier says the GCC is not advocating for widespread use of herbicides.

“If native species don’t come back at the rate that we expect, then we might not consider doing it again,” he said.

The GCC is currently working to develop more outreach about herbicide use and the GCC’s work. Education events like an expert panel and collaborating with Pollinator Friendly Greensboro for mechanical removal have been suggested during the public meetings. 

“It’s really easy to devolve into animosity”, said Marlier, about the local debate over herbicide use. “I wanted to be clear that this was a conversation that encompasses a wide range of belief systems, and that there is room for ongoing conversation and communication.”

Via Community News Service, a University of Vermont journalism internship, for The North Star Monthly