Onota Lake will be open on Tuesday — a day after an herbicide was applied to control weed growth (2024)

This story was updated at 5 p.m. Tuesday, June 18, 2024 with comments from Berkshire Environmental Action Team.

PITTSFIELD— The city’s senior park official says an herbicide applied to Onota Lake on Monday poses no hazard to residents seeking relief from expected heat and humidity at Burbank Park.

Seventy-five of Onota’s 617 acres were treated with ProcellaCOR, an herbicide targeting the lakes prolific Eurasian milfoil. The lake was closed Monday, but will reopen Tuesday, as the city Health Department’s heat advisory takes effect. High temperatures are expected in the 90s.

“There’s no concern for swimmer safety following treatment of the lake,” said Jim McGrath, the city’s open space and natural resource program manager. However, swimming at Burbank Park and at Pontoosuc Beach remains “at your own risk,” as lifeguards are not yet on duty.

Boating and fishing may resume Tuesday as well. Use of the lake for agricultural irrigation— watering lawns, gardens or plants of any kind— is prohibited for eight days post-treatment, but McGrath said he isn’t aware of any such use by property owners.

Eurasian milfoil is an invasive species that crowds out native plants and disrupts underwater ecosystems and recreation. It has been a problem in Onota Lake for generations, and over the years the city has applied herbicides to reduce the weed's grip on the lakebed.

“We have high confidence that the work being done here today is safe for the ecosystem,” McGrath said of Monday’s application of ProcellaCOR. “We’re simply targeting large dense beds of Eurasian milfoil in an attempt to eradicate those plants, and to encourage native plants to come back.”

Onota Lake was quiet Monday, and strangely empty for a sunny, June mid-morning. By 10 a.m. Berkshire Community Rowing’s members had wrapped up their morning workout, and city employees on duty ensured there were no anglers on the water or casting from shore.

Meanwhile, Vinnie Notaro of Solitude Lake Management had his flat-bottom airboat and its Chevrolet eight-cylinder engine on the boat ramp and ready to go. Shortly after 10 a.m., he edged the boat into the water, then headed north for the first application along the lake’s eastern shore.

Onota Lake will be open on Tuesday — a day after an herbicide was applied to control weed growth (1)

The state set areas of the lake’s northwest shore and the neck of Thomas Island as off limits for herbicides, due to the presence of rare plant species in those locations. McGrath said Notaro would know to steer clear of those areas because the map data was uploaded into his GPS.

“It helps us to stay very accurate with our treatments,” McGrath said. “We want to just target milfoil. We also don't want to waste the chemical because it's very expensive ... on the order of $150 an acre.”

Of the 75 acres treated Monday, 47 were provided under warranty, as previous treatment of the lake proved ineffective, McGrath said.

McGrath said using an aquatic weed harvester— a floating mower that cuts the weeds below the surface— just doesn’t make sense for controlling milfoil on Onota. “It's somewhat impractical here because of the size of this lake. And it's very costly,” he said.

Brittany Ebeling, the deputy director of Berkshire Environmental Action Team, said the group generally opposes the use of herbicides and pesticides, and specifically opposes chemical treatment of Onota Lake "to suit human recreation preferences."

ButEbeling was also concerned that the notices posted by the city did not specify what chemical it intended to use, and that notice of the Monday treatment was posted on the city website on Friday.

"It's so critical that community members be engaged in the conversation about how we deal with the stewardship of natural resources,"Ebeling said. "To receive an announcement made by the city on a Friday and have 'go time' on a Monday concerns me."

ProcellaCOR is described by its manufacturer, SePRO Corp. of Carmel, Ind., as “a selective systemic herbicide for management of freshwater aquatic vegetation with little or no continuous outflow.”

Onota Lake will be open on Tuesday — a day after an herbicide was applied to control weed growth (2)

The U.S. Environmental Protection Agency granted ProcellaCOR “reduced risk” status in 2017, based on data showing based on acute exposure, it is largely nontoxic to mammals, birds, fish, reptiles and bees. However, pushback from residents near Lake Bomoseen, in central Vermont, led the state to permanently ban the herbicide from use there. A pair of groups in upstate New York are opposed to its use in Lake George.

The chemical is a synthetic auxin— a human-made plant hormone that regulates plant functions such as development and growth. According to a 2019 review conducted jointly by the Massachusetts Department of Environmental Protection and the state Department of Agriculture, "Having insufficient auxin concentration stunts growth while having too much can cause cell wall damage, leading to death. Thus, these effects can be exploited in developing effective herbicides.”

That same review said testing on carp “showed no mortalities” and showed sub-lethal effects on fish, including lethargy and difficulty maintaining equilibrium.

Onota Lake will be open on Tuesday — a day after an herbicide was applied to control weed growth (3)

Minnesota regulators, however, warned that oxygen depletion resulting from decomposing weeds could result in fish suffocating under certain conditions.

The Massachusetts review said the formulated mixture does not not persist in the environment “as dispersion, dilution and degradation processes take place.” It advised that ProcellaCOR not be used in estuaries, saltwater environments or freshwater systems directly flowing to estuaries or marine waters, and that applications be made “from a boat or ground equipment,” as was the case on Onota Lake on Monday.

Onota Lake will be open on Tuesday — a day after an herbicide was applied to control weed growth (2024)
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