Tag Archives: invasive aquatic species

TOP STORY: Fight Against Hydrilla Advances with Increased Public Information, Focus on Herbicide Safety

Posted on by
This comparison provided by the U.S. Army Corps of Engineers shows how hydrilla spread in Hamburg Cove between 2019 and 2024. The cove is on a list of sites to be treated with herbicide as part of a pilot project once funding and permitting comes through. Selden Cove, which received an herbicide application last year, will receive another this month.

LYME, CT—With the town firmly entrenched on the front lines of the fight against the uniquely pernicious water weed known as hydrilla, federal authorities on Wednesday held a virtual public information session on their efforts to help local communities control the invasive plant using herbicides. 

The Connecticut River Hydrilla Research and Demonstration Project, led by the U.S. Army Corps of Engineers (USACE), first came to Lyme’s Selden Cove in 2023 to apply a red dye mimicking the flow of herbicide. The lessons learned set the course for the following year’s treatment of dipotassium of endothall in the same area.

Ben Sperry, research biologist with the U.S. Army Engineering Research and Development Center, described Selden Cove as a unique site compared to four other water bodies in the pilot program that used different herbicides. 

“We used endothall alone, got pretty good control of hydrilla, but the water exchange in Selden Cove is quite rapid,” he said. “Consequently, hydrilla has already come back this year up to 60% occurrence, closing in on pretreatment levels that we saw in 2024.” 

That’s when mats of hydrilla were so thick that waterside property owner Joe Standart said the cove was impassable to his power boat and to the sport fishermen who used to come around. 

Project documents show the cove will be retreated the week of Aug. 18. But a plan to treat 12 additional sites – including Hamburg Cove, Joshua Creek and Selden Creek – will not happen this year due to federal funding limitations. 

Hamburg Cove, however, will run red sometime between Sept. 15 and 19 as scientists return with the flourescent tracer dye administered by a certified contractor to gauge which herbicides, and how much of them, to use next year. 

The Army engineers’ project is intended to gauge the safest, least toxic way to stem the hydrilla infestation choking off many areas of the river and being carried on the bottom of boats into lakes throughout the state. 

Keith Hannon, USACE Project Manager, said the agency’s ultimate goal is to pass along the information from 17 test sites to state and local governments so they can address the problem on a larger scale. 

Scientists describe the strain of hydrilla affecting the Connecticut River as genetically distinct from the one that emerged in the 1950s after a tropical fish dealer in Florida allegedly dumped an aquarium into a Tampa canal. It’s also removed from a second strain that emerged in the 1980s in the Potomac River.

The name comes from the Hydra serpent of Greek mythology, according to Hannon. 

“When you cut off one of its heads, it would grow two more in place,” he said, describing the trait that can be seen in its namesake’s ability to break off easily into new plants. 

Diquat Fears

It was over a month ago that an herbicide called diquat was launched into the internet’s viral vernacular by a rap artist originally from Fairfield County who started posting on social media about the chemical’s toxicity and a lack of government transparency. 

An online petition from Chris Webby, which to date has amassed 20,112 signatures, calls on authorities to discontinue the use of the diquat while focusing on “non-toxic, mechanical and biological alternatives” to manage the plant. 

Hannon during the virtual presentation said Sperry’s group has been studying the various ways to remove invasive aquatic plants for decades. Methods range from mechanical, like hand pulling, to biological, like using grass carp or weevils to kill the weeds.

“We know the effects and usefulness of those other mechanisms,” he said. “So we wanted to understand the use of herbicides on this new strain, because it’s unknown as to how effective that would be. But we know how effective the other methods could be. And how costly they are.”

He cited data from the Chester Boat Basin showing the cost to bring in a mechanical harvester three times during the summer cost $14,190, compared to $4,475 for an application of herbicide lasting for the season.

Hannon said hydrilla has the potential to wreak havoc on recreational opportunities, the tourism industry and aquatic habitats. 

Local Concerns

Diquat is among the herbicides under consideration for Hamburg Cove, Joshua Creek and Selden Creek once funding and permits are secured, according to project documents.

Staff and board of directors members from Camp Claire during the presentation posed questions about safety. 

Carol House, who identified herself as a board member at the Lyme-based camp, asked how long the herbicide poses a concern for children in the water. 

Sperry, the research biologist, said there are no fishing or swimming restrictions associated with any of the herbicides being used on the project. 

“We do prefer that recreational users kind of stay out of the way during treatment, just for boat safety,” he said.  

Hannon said signs, like the one posted last year on a dead log at the entrance to Selden Cove during treatment, go up on the day of treatment but are not required to remain. 

Anne Overstreet, with the U.S. Environmental Protection Agency’s Office of Pesticide Programs, said the results of the agency’s most recent evaluation of diquat in 2019 were published the following year as part of a regulatory framework designed to ensure there are no unreasonable adverse effects to human health or the environment. 

“And there is no risk of concern for adults or children exposure to diquat from swimming immediately after application, from inhalation, contact with water, or potential incidental swallowing of the treated water,” she said. 

She acknowledged “mild toxicity” to fish and other aquatic organisms. 

“We look at a tremendous number of studies and we look at points of departure where effects are actually seen at very high doses in laboratory studies. And then we choose the dose that is ‘no-effect’ – where no effects are found. And then we regulate a thousand times below that threshold,” she said. “So there are no effects that would be seen.” 

She said risks to those applying the chemical can be mitigated by following directions on the product label calling for precautions like eye protection. 

“We ensure that folks that mix and load and pour those products also use respirators to protect from possible inhalation of the concentrated product before it is applied,” she said. 

Responding to a question about using treated water to irrigate crops, Overstreet advised that, “If it isn’t toxic from a dietary standpoint from ingestion, then utilizing it for irrigation of crops would also not be a concern.” 

Selden Cove

Sperry during a media briefing following the public presentation said endothall was the herbicide of choice for Selden Cove after the dye tests determined how quickly water moves through the inlet. Endothall worked best because it stays effective for the right amount of time and is safer for native plants.

Included in Wednesday’s virtual presentation by the U.S. Army Corps of Engineers were photos from Selden Cove to illustrate the extent of the hydrilla infestation prior to treatment.

Fast-acting diquat by itself is not effective on hydrilla, according to the biologist. 

“With the plants that we were dealing with in Selden Cove, we felt that diquat would have been less selective and maybe not as effective as endothall at the rate that we chose to treat with,” he said.

Hannon said the delay in treating the 12 additional sites is not related to the public diquat pushback.

Earlier, he cited federal budgeting constraints exacerbated this year by the threat of a government shutdown and related costcutting measures, as well as permitting constraints. 

“We would be at this point regardless of any pushback that came about,” he said.

TOP STORY: Controlling Hydrilla is Critical to CT River’s Health, Best Way to Implement Control Now Heated Discussion Topic

Posted on by
This photo was taken September 2020 during an inspection of Whalebone Cove in Lyme, in which it was found 60 to 70% of the waterways were clogged with hydrilla vines.

State Legislators say “There has been false and misleading information on social media” about use of herbicide diquat to combat Hydrilla growth in CT River

LYME, CT—Reactions to the use of herbicides in the fight against hydrilla along the lower Connecticut River have only recently begun to spread across social media, but the topic is old news to local property owners long concerned with the pernicious water weed. 

Joe Standart, a Selden Cove resident, said the herbicide treatment applied last year as part of a U.S. Army Corps of Engineers (USACE) project worked “beautifully” to rid the cove of a strain of hydrilla unique to the Connecticut River. 

“There’s no trace of hydrilla at the moment,” he said in a phone interview Wednesday. For four years prior, fast-growing and thick mats of the aquatic weed had rendered the water body impassable to power boats and inhospitable to many fish and native plants during the height of summer. 

Efforts to plan the next phase of the Connecticut River Hydrilla Research and Demonstration Project are ongoing despite federal funding limitations exacerbated this year by the threat of a government shutdown and related costcutting measures. 

Keith Hannon, USACE Project Manager, said Selden Cove may get another treatment this summer using money approved by lawmakers in the previous budget. But a proposal to add Hamburg Cove and Joshua Creek to the treatment mix, along with additional chemicals, will not happen this year. 

Meanwhile, critics of the state and federal effort to bring hydrilla under control – including a rap artist originally from Fairfield County, whose online petition has amassed 18,839 signatures to date – have gone viral with concerns about toxicity and a lack of government transparency. 

The petition calls on authorities to discontinue the use of the herbicide diquat dibromide while focusing on “non-toxic, mechanical and biological alternatives” to manage the plant. 

Documents from USACE engineers show the treatment last year in Selden Cove consisted of Dipotassium salt of endothall, while sites in four other towns along the river were treated with chemicals including diquat. 

A proposal for 12 additional sites currently under review specifies diquat is slated to be used in Hamburg Cove and Joshua Creek. 

Diquat is approved by the U.S. Environmental Protection Agency (EPA) and state Department of Energy and Environmental Protection (CT DEEP), according to Hannon. He said EPA approvals are based on field and laboratory studies that show the active ingredient doesn’t cause unreasonable risk to humans or the environment. 

He said the threat of the genetically distinct strain of hydrilla is real.

“It spreads quickly and aggressively, forms dense monoculture mats of the plant that block light which native plants need, prevents fish passage and boat traffic during the summer months, threatens native aquatic plant species by displacing them, and threatens the local river tourism and recreation economy, among other negative effects,” Hannon said. 

It can also lower property values and increase an area’s flood risk, the USACE said in a statement.  

A Public Statement issued July 8, led by State Representative Renee LaMark Muir and signed by 18 state legislators states, “There has been false and misleading information on social media that has triggered fear among residents about the use of the herbicide diquat to combat the growth of Hydrilla in the Connecticut River.”

The Statement continues, “If we do not act now, the ecosystems of the Connecticut River will be changed forever, and the river may never recover. Understandably, the use of any chemical in our environment causes concern. If we do nothing, the Hydrilla problem will worsen, and other invasives will proliferate.”

Congress allocated $5 million in 2024 and $6 million in 2023 to address hydrilla in Lake Champlain and the Connecticut River, and in 2022 authorized $1 million for the Connecticut River. 

At the state level, the Office of Aquatic Invasive Species was created in 2022 with roughly $600,000 in funding annually. 

Selden Cove, Pameacha Pond in Middletown and Petzold’s Chester Boat Basin remain the only sites that may be treated this year amid budget constraints, according to Hannon. A public notice will be posted to the project website once a treatment schedule has been determined.

An informational meeting on the proposed modifications affecting Lyme was held at the Town Hall in April. Comments on the project will be accepted through July 13 at CTRiver-Hydrilla@usace.army.mil. 

Natural Limitations

The project, overseen by the USACE in partnership with the Connecticut Agricultural Experiment Station and other organizations, began several years ago to figure out which aquatic herbicides ― and how much of them ― are best suited to fighting off the uniquely pernicious aquatic species.

Scientists in 2023 applied red dye to Selden Cove to mimic the flow of herbicide. It was a precursor to last year’s treatment meant to gauge the safest, least toxic way to stem the problem. 

Standart, who has spoken with scientists from his property at Selden Cove and has looked into the issue himself, said he was assured herbicides are carefully chosen based on the characteristics of each water body. He has also come to see it as the only effective option. 

He said pulling out hydrilla by hand doesn’t work because roots remain in the sediment and broken fragments can rapidly sprout new plants in new locations. 

Hannon pointed to the limitations of other natural options. 

He said introducing fish like grass carp – which he described as difficult to control, monitor and remove from the system – means beneficial native plants would be consumed in the process. And installing man-made mats to block the light would also kill off native plants – if it were feasible to cover such large areas, which Hannon said it is not. 

“Other methods to control the plant have been considered, but they do not work to effectively control hydrilla,” Hammon said.  

Standart said all signs of hydrilla disappeared within about a week of the herbicide application last August. But other forms of vegetation beneficial to the cove remained. 

“It’s still a very healthy ecosystem with wild rice and other things,” he said.

Editor’s Notes: (i) Visit this link to read more information about hydrilla from the U.S. Army Corps of Engineers is available here. For more facts on the USACE and ERDC’s efforts to eradicate Hydrilla, visit this link. 

(ii) The statement signed by the legislators states, “We can all help slow down the spread of this invasive and highly transmissible strain of Hydrilla and other invasive plants. CT DEEP and USACE recommend the best way is to “Clean, Drain, Dry” your boats and any type of watercraft and fishing gear after removal from the river or a lake. Report any sightings of the strain to DEEP at this link or to the Connecticut River Conservancy at this link.”