SALISBURY— A fierce and costly battle to halt the spread of hydrilla in East Twin Lake may have finally paid off.
All but three remaining small patches, one near the shoreline at O’Hara’s Landing Marina and two others in deeper water as boats exit the marina and head out, have been destroyed by this summer’s treatment with the aquatic herbicide fluridone, which began on May 20. None of the remaining plants are thriving.
“We hit 90 days in mid-August, and most of the hydrilla is dead,” reported Dominic Meringolo, an environmental engineer with SOLitude Lake Management, whose company was retained by the Twin Lakes Association (TLA) to apply the lake’s 2025 herbicide treatments.
The announcement was met with relief and applause from the approximately 100 members of the Twin Lakes Association who attended the group’s annual meeting Aug. 2 at Isola Bella.
“This is the first good news we’ve had in three years with hydrilla, but we’re far from being able to say that the coast is clear,” said TLA President Grant Bogle.
He stressed that vigilance is required and Northeast Aquatic Research (NEAR), the TLA’s limnologist, will continue to do detailed plant surveys throughout the lakes. “In East Twin, we supplement these with diver-assisted surveys in the deeper water, which are expected to take place in late August or September.”
Russ Conklin, vice president of lake management for the TLA concurred. “We are going to have to do this two, three more years, or maybe longer.”
According to TLA officials, experience from past eradication and control efforts is that this is a multi-year endeavor. Left untreated, hydrilla has returned in lakes like Coventry Lake, which took a year “off” from treatment.
“The fact is,” said Bogle, “We don’t know how long we will need to continue treating the East Bay, but by keeping it in control in this section of the lake, we are attempting to keep it from spreading further both within Twin Lakes and as boats exit Twin Lakes.”
Possibly spread by fishing boats
The battle to stop the spread of the robust Connecticut River variant of hydrilla in East Twin began in the fall of 2023, when it was discovered near the marina, and had since ventured further out into the lake.
At the time of its discovery, East Twin was the first lake in the state outside of the Connecticut River, where it had been wreaking havoc, to have identified the virulent strain in its waters.
Gregory Bugbee, associate scientist at the Connecticut Agricultural Experiment Station (CAES), where he heads the Office of Aquatic Invasive Species (OAIS), was the first environmental expert to visit East Twin after the TLA’s limnologist, George Knocklein, found the stringy, dark green plant, which looks similar to the native waterweed, elodea.
“We got out there within a week, got our boat out on the lake and sent out DNA analysis confirming the Connecticut River strain,” recalled Bugbee who, along with Meringolo, were guest speakers at the TLA meeting.
“How did it get from the river into East Twin? Fishing tournaments were in the river and some people went to O’Hara’s for a tournament here,” the CAES scientist noted.
He said the Connecticut River strain had likely been around for “many, many years” before hydrilla was detected and was thought to have been contained to the river.
“But that all changed with East Twin Lake in 2023, when George Knocklein found it floating around O’Hara’s Landing Marina,” said Bugbee.
Since then, he noted, nine additional lakes have been invaded by the rapidly growing water weed. To date, they have been met with limited success in knocking back hydrilla.
Among a few of the lakes’ attempted remedies to rid hydrilla include the introduction of sterile grass carp, hand-pulling or raking them.
“Pulling it is not effective,” said Bugbee, a certified diver, who tried the method. “We went back a month or so later and the hydrilla had all regrown.”
Another lake group sponsored a “Take a Rake to the Lake Day,” where a $500 prize was offered to the person who raked the largest haul of hydrilla out of the water.
“I said, I’ve got to see this, so I went out in my boat,” said Bugbee, who recounted with humor the vision of a woman raking hydrilla into a wagon. The winner, he recalled, removed 750 pounds of plant and muck.
While the event was unsuccessful in eradicating the invasive weed, he said it did bring the problem to the forefront of people’s attention and eventually was tackled with herbicide treatments.
The immediate impact of the herbicide on native plants is being assessed by NEAR.
“We know that outside the treatment area, the plants are doing fine,” said Bogle. “We will have more definitive information on the native, rare and invasive plants at our scientific coalition meeting in the fall.”
Meanwhile, the U.S. Army Corps of Engineers (USACE) has been working for 7 years now doing trials with herbicides, said Bugbee.
“USACE does the research then turns it over to the states. We are doing boat launch surveys on all the boat launches in the state looking for hydrilla. If we can find it by the boat ramps, we can suggest management, potentially.”
The good news is, it works
Conklin noted that other than the few surviving hydrilla, “there are no other plants that George has found in that bay” where herbicide was applied. “We were able to get there, and it only took us three years.”
Fluridone treatments were calculated based on the entire volume of the east basin of East Twin and slow-release pellets were applied to the littoral zone. The pellets release over a period of six to eight weeks, with peak release at two to three weeks after application.
Liquid fluridone was used during the first three applications to boost initial concentration, followed by slow-release pellets, according to Meringolo. The goal, he explained, was to use the herbicide at between three and five parts per billion for approximately 120 days.
Because by the 90-day mark most of the hydrilla had died, Meringolo said there are no plans to continue the last two treatments, as the slow-release pellets will remain in the water close to the 120-day target.
Conklin agreed. “Why should we be killing dead plants? Let’s see what happens this year. The good news is, it works. The bad news is, we’ve got to do it again.”
The TLA official noted that a dose of good fortune was also on the TLA’s side.
“We were fortunate that George found it over here in the bay,” where the water is relatively stagnant. If we found it out in the middle lake or third lake, we would be hard-pressed to be able to do this treatment.
