Hydrilla’s ‘alarmingly rapid’ spread prompts state survey of boat launches

SALISBURY — Last summer, East Twin became the first lake in the state to discover the presence of a genetically distinct strain of invasive hydrilla, a robust aquatic plant which, if left unchecked, can out-compete native plants and devastate local ecosystems.

Until it found its way into East Twin, most likely by hitchhiking a ride on a boat or boat trailer, the novel variant had only been identified in the Connecticut River, where it has wreaked havoc since 2016, and continues to do so today, as scientists and environmentalists work furiously to find a way to manage and eradicate the aggressive weed from the state’s waterways.

In response to the growing threat, the state environmentalists plan to spend the next several months, the peak hydrilla growth period, surveying 94 state-owned boat launches throughout Connecticut in search of hydrilla, according to Jeremiah Foley, assistant scientist and biological control specialist with the Connecticut Agricultural Experiment Station/Office of Aquatic Invasive Species (CAES/OAIS).

Foley, who has paid numerous visits to East Twin, was the guest lecturer at the Aug. 3 annual meeting of the Twin Lakes Association (TLA) at Camp Isola Bella. His presentation focused on the status of hydrilla in Connecticut and specifically on Twin Lakes.

He noted that a novel strain of hydrilla, first found in 2016, infests the Connecticut River from Agawam, Mass., to near Long Island Sound.

“In 2023, molecular identification confirmed the plant was also in six Connecticut lakes and ponds, and in four of the lakes, the hydrilla was found in close proximity to public boat launches. This suggests the plant may be introduced by launch activities particularly by boats entering the lakes that had previously been in the Connecticut River,” Foley explained.

The state scientist said early detection and rapid response protocols would be enhanced if hydrilla surveys of areas near boat ramps were performed to quantify how common the Connecticut River variant of hydrilla is found near boat launches, and if so, “provide guidance to help boaters prevent introduction, and prioritize management decisions.”

The boat launch survey project, he said, will include all 94 state-owned boat launches, including launches located at lakes and ponds. Seventy-five of the sites accommodate trailers and 20 are only for car top/carry in, he explained.

East Twin was first lake in state to find hydrilla

“We have now found the Connecticut River hydrilla in several locations,” explained Foley, who, before joining the OAIS, worked on invasive species control and eradication, including hydrilla, in Florida, where his bread and butter, he said, was biological control.

“You guys were the first to get it, or the first to find it. This year alone, we found it at four more sites. I can’t even keep my data updated fast enough. We are in the middle of a fight right now with hydrilla, and each punch definitely hurts a little more.”

During the nearly two-hour meeting, Foley, TLA officials and Salisbury First Selectman Curtis Rand fielded concerns and questions from those in attendance, many of whom live or own property on the Twin Lakes. They discussed the importance of halting the spread and eventually eradicating hydrilla through aggressive monitoring and lake management.

TLA president Grant Bogle opened the meeting by noting that it was no surprise that the 2024 survey revealed hydrilla has spread at East Twin. “We should be expecting this for a few years until we get control of the situation,” he noted.

Hydrilla, which is among the most aggressive invasive aquatic species, able to grow in water up to 30 feet deep and double in biomass every two weeks, has taken root in three new locations along East Twin’s eastern shore, at the north bed and has formed deep mats around the boat launch.

“If you go down to the marina, look to the right and look to the left, it’s hydrilla. It’s everywhere down there. That’s ground zero,” said Bogle.

On a positive note, the TLA president explained that the state is allowing the expanded use of the herbicide Sonar, widely regarded as one of the most effective treatments, around O’Hara’s Landing Marina and further into the north cove, where the plant is rapidly growing.

The treatment area around the marina will expand to include 17 acres, according to Russ Conklin, vice president of lake management for the TLA. Treatments were expected to start Aug. 7.

Coventry Lake: a model of success

Looking ahead to next year, TLA officials said they plan to start Sonar treatment earlier in the season and for the entire growing period, and treatment will cover the entire littoral zone of East Twin, rather than spot-treatment, a strategy that was met with success at Coventry Lake, in Tolland County, where hydrilla was discovered in 2015.

East Twin officials are looking to Coventry Lake’s success in eradicating hydrilla after a seven-year effort as a case study for East Twin, even though that lake’s strain of hydrilla is slightly different than the Connecticut River variant.

Coventry initially spot treated with an herbicide Aquathol and applied a subsequent five-year treatment of Sonar to its entire littoral zone. By the end of 2022, there was no evidence of hydrilla in the lake. No herbicide treatment was applied in the 2023 season, and after three hydrilla beds cropped up in August, their lake consultant, Northeast Aquatic Research (NEAR), recommended a return to Sonar treatments of the entire littoral zone for a minimum of three years.

“There is a lot of ignorance surrounding the use of herbicides…that you can put the product in the water and see it go downstream. That’s not the case. You can be selective,” Foley explained.

He noted that there are a dozen products highly regulated by the EPA, and that herbicides are just one tool within the tool belt of dealing with invasive plants.

“If you don’t do anything, that’s also a threat to that biodiversity,” said Foley.

‘Everyone is scared to death about expenses’

As hydrilla grows, lake management costs soar, too.

Bogle said the TLA expects to spend $300,000 battling hydrilla this year, and $350,000 in 2025.

“Maintaining Twin Lakes for future generations,” he said, “requires us to commit to sustained investments of upwards of $350,000 per year.” For the 2025 season, Bogle said the TLA needs to raise upwards of $225,000 per year.

The bulk of responsibility for funding lake management will fall to the TLA membership, he noted, as annual membership dues account for less than 10 percent of the budget.

“Everyone is scared to death about these expenses. And here is the unfortunate news,” said Bogle. “It doesn’t go down next year or the year after that.”

The town of Salisbury is poised to contribute $100,000 for lake management in 2025 which includes the cost of launch monitors at the marina, he said, and the TLA will continue to explore other funding sources, including grants through DEEP.