Portland will follow through on a proposal to use pesticides to destroy browntail moths in Deering Oaks despite objections by a citizens group that pushed the city to implement strict rules on pesticide use.

Members of the city’s parks department told the City Council Wednesday about the plan for curtailing the insects, which threaten the health of both the park’s trees and humans who are sensitive to the larvaes’ tiny, poisonous hairs.

Tree canopies will be sprayed with either an organic or synthetic pesticide during the week of May 20, and the park will be closed for one or two days. The Portland Farmers Market will be relocated to Payson Park for six weeks and other large scale gatherings and events planned for late May and June will be postponed until early to mid-July.

Deering Oaks will remain open for sports, pedestrians and visitors, but warning signs will be posted.

An exemption in the city’s pesticide ordinance will allow the department to spray the trees without council approval.

But Portland Protectors, a citizens group instrumental in a 2018 effort to place restrictions on pesticide use in Portland, issued a statement Wednesday objecting to the use of synthetic pesticides. Councilors took no action at their Wednesday night workshop, but expressed confidence in the parks department’s ability to protect trees and public health.

“This (spraying plan) will not come before the City Council for a vote, but we thought it critical enough to bring it before you,” City Manager Jon Jennings told councilors.

Parks officials said browntail caterpillars emerge from their webs in late April or early May to begin feeding on foliage, which can eventually kill a tree. That time period is also when the caterpillars shed their hairs, which become airborne and can be a skin irritant.

“The population has been escalating for the past three years,” said Ethan Hipple, director of Parks, Recreation and Facilities. “It’s got to the point where we need to take more assertive actions.”

The city said manual removal of webs is nearly impossible because many webs are located in treetops that are so tall city equipment cannot reach them. Some trees have as many as 1,000 webs, each containing 200 to 400 caterpillars.

Hipple would not commit to whether the department will use organic or synthetic pesticide.

“We are exploring all of our options,” Hipple said.

Avery Yale Kamila, co-founder of Portland Protectors, sent a statement Wednesday to councilors urging them to reject the spraying plan or use organic pesticides if webs can’t be clipped manually.

“Portland Protectors urges you to reject this proposal and instruct Parks and Rec to hire a company to clip the webs ASAP. If a pesticide must be used this spring, we urge you to instruct the department to use an organic-approved pesticide and to conduct spot treatments not broadcast spraying or misting, which is the high-risk treatment plan from Parks and Rec,” the statement said.

Kamila said synthetic pesticides used to kill browntail moths pose a high risk to pollinators as well as aquatic organisms. Deering Oaks is at sea level and drains into Casco Bay. She said lobstermen have opposed the use of some of these pesticides because they can harm lobsters and damage shells.

Kamila said there are organic approved pesticides used to treat browntail moths that tend to pose lower health risks to humans. In 2017, school officials in Freeport treated browntail moth nests in oak trees near athletic fields at local schools with an organic pesticide in response to parents’ concerns.

City Councilor Spencer Thibodeau said he views the browntail moth infestation as a threat to Deering Oaks’ majestic oak trees, many planted more than 200 years ago.

“We hold this park in the public trust and we have an obligation to do this,” Thibodeau said.

“Keeping the trees at Deering Oaks healthy is so important. They are such as beautiful asset,” Mayor Kate Snyder said.

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