East Twin Lake tackles hydrilla, shares what worked

“Forevermore we are going to have to be hyper-vigilant. It came in once and it could come in again.”
—Grant Bogle, president of Twin Lakes Association

SALISBURY — An aggressive and costly three-year battle to rid East Twin Lake of a genetically unique strain of hydrilla that chokes lakes and obliterates native plants appears to have finally paid off.

“The good news is, the hydrilla is pretty much gone. We have not found anything,” George Knoecklein of Northeast Aquatic Research (NEAR), the Twin Lakes Association’s limnologist, reported during its fall coalition meeting of local, state and federal scientists, environmentalists and stakeholders on Tuesday, Oct. 8, at O’Hara’s Landing Marina.

The meeting’s location — several yards from where the first strand of the pernicious plant was discovered at the marina in May of 2022 and where a large sign now warns boaters of the threat — was a fitting backdrop for the 90-minute coalition meeting focused on managing the aquatic invader.

It is believed that the invasive weed, known as the Connecticut River Hydrilla, was introduced by hitching a ride with an unsuspecting boater.

Coalition partners included scientists and officials from the Connecticut Department of Energy and Environmental Protection (DEEP), the U.S. Army Corps of Engineers, local lake associations, town and state officials and other stakeholders.

Three years ago East Twin became the first lake to discover the novel Connecticut River strain of hydrilla in its waters. Since then, it has been identified in 10 additional state lakes.

Coalition member Gregory Bugbee, associate scientist at the Connecticut Agricultural Experiment Station’s Office of Aquatic Invasive Species (CAES/OAIS), reported that an effort to inspect all 84 boat ramps in Connecticut this year yielded only one site where hydrilla was found.

The threat nonetheless has lake associations rattled. Several groups from around the Northwest Corner have turned to the TLA and its coalition for guidance, as hydrilla — once established — is notoriously difficult to eradicate.

Herbicide’s impact

The meeting centered on this past summer’s success as well as collateral damage to a native plant, water marigold, following the TLA’s whole-lake treatment with the herbicide fluoridone.

Domenic Meringolo, environmental engineer and project manager with SOLitude Lake Management, said this summer’s treatment with Sonar, SePRO’s flagship aquatic solution, was more successful than prior spot treatments using the systemic herbicide ProcellaCOR.

While the ProcellaCOR failed to kill hydrilla, it was “beautifully effective” on ridding the lake of Eurasian watermilfoil, said Knoecklein. “It became pretty clear that the whack-a-mole strategy wasn’t going to work” on hydrilla.

The SOLitude project manager noted that the two-to-five parts per billion (ppb) concentration of fluoridone used throughout this summer at East Twin was to selectively control hydrilla while minimally affecting native aquatic plants at low concentration.

While the Sonar destroyed the hydrilla, it had an unintended ecological impact on one of the lake’s native aquatic species, Bidens beckii, commonly known as water marigold. The Bidens is a state protected plant that had been growing profusely in East Twin.

“This year, we couldn’t find it,” reported NEAR’S Knoecklein.

Of the 54 species of aquatic plants documented in East Twin Lake, the Bidens beckii was the only one adversely affected by the treatment, he explained. “We have more of it in Middle Twin, and there’s a very good indication that nothing else was impacted here.”

Knoecklein said he has been in contact with DEEP’s Natural Diversity Database (NDDB) regarding the loss of Bidens beckii.

“It was not completely unexpected, but we’ll be watching very closely next year,” he said. “I am hoping for some recovery.”

A diver is expected to re-inspect the lake this week.

“The hydrilla game has really become both surface visualization and looking for hydrilla in deeper waters,” said Knoecklein. “You can’t combat hydrilla in a lake without using these strategies.”

The TLA limnologist noted that prior dives found both young hydrilla plants and larger established ones.

“My suspicion is that this has been in the lake for four years and turned into a fort during that time, with massive plants six feet tall and lots of shoots. We had to move water lilies to find hydrilla growing under those plants.”

A sign warning boaters of the hydrilla threat at O’Hara’s Landing Marina stands in the location where the invasive weed was discovered at East Twin Lake in May of 2022. Debra A. Aleksinas

Lessons learned, lessons shared

The forum touched on the soaring costs of lake management, a concern to the TLA as well as smaller lake groups with limited funds and resources.

TLA’s annual lake management expenditures have increased tenfold — from about $50,000 per year to as much as $500,000 for the foreseeable future — as the association continues its intensive monitoring, testing, and prevention efforts.

Despite those costs, officials emphasized that East Twin’s experience offers valuable lessons for other lakes confronting hydrilla for the first time or preparing for an invasion.

Representatives from the Lake Wononscopomuc Association and Mt. Riga Inc., in Salisbury, attended the fall coalition meeting, along with officials from Mudge Pond Association in Sharon and Doolittle and Benedict Pond in northeastern Norfolk.

Christina Astrove, lake board president representing Doolittle and Benedict, was a first-time attendee. She was hoping to learn about how the TLA has been dealing with hydrilla and what steps are being taken to control and eradicate the worrisome weed.

While her lake community is private and prohibits motorboats, she is “very concerned” about the looming threat.

“I attended a Connecticut Federation of Lakes meeting this spring and have taken several webinars” on the topic, noted Astrove. “It’s scary.”

Mudge Pond representative Andrew Cahill said his group is bracing for hydrilla’s arrival due to high boat traffic.

“We have everything but hydrilla at this point, but I’m sure we will have it at some point.”

TLA President Grant Bogle said he is pleased to share information from lessons learned. “The goal is not only to support Twin Lakes, but to spread the word. It takes a village, literally, to address this threat.”

TLA officials said they have been fielding calls from lake associations throughout the United States seeking advice and guidance, and they are happy to share.

CAES’ Bugbee praised the Twin Lakes group’s aggressive response to the hydrilla threat, swift creation of its coalition of advisors and for sharing their collective knowledge. “This organization is second to none. It’s almost like a poster child for how things should be done.”

Knoecklein said despite vigilant surveillance of boat ramps and closing lakes off to the public, the hydrilla threat persists.

“In my opinion all possible vectors are on the table,” including recreational fishing and birds flying overhead dropping plant fragments.

Grant Bogle, TLA association president, agreed that “surveillance is key.”

“While we have good news to report in terms of hydrilla, this isn’t over. Forevermore we are going to have to be hyper-vigilant, no matter what happens down the road. It came in once and it could come in again.”