An herbicide used to treat hydrilla, an invasive plant in Connecticut lakes, ponds and rivers, has recently been the target of social media posts circulating online.
Diquat, the common name for diquat bromide, is a federally-approved herbicide used to control grassy weeds in aquatic areas, according to the Environmental Protection Agency.
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The U.S. Army Corp of Engineers (USACE) New England District decided to use diquat and two other herbicides to combat the growth of hydrillas after two years of testing and research.
NBC Connecticut has reported on hydrillas and its disruption to the ecosystem since it was found in Connecticut a decade ago.
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Hydrilla forms thick stands, or mats, in freshwater lakes, ponds and rivers. It typically grows in shallow fresh water up to approximately 40 feet deep, depending on water clarity.
According to USACE, hydrilla can disrupt, slow down or divert water flow. It increases the water’s pH, and it outcompetes and replaces native aquatic plants.
Hydrilla also clogs up bodies of water, making boating difficult.

“Sometimes it’s so thick, it’s hard to get through,” said Alicea Charamut, the executive director of Rivers Alliance of Connecticut, a nonprofit that works to protects the state’s rivers. “It has taken over a lot of the marinas along the Connecticut River.”
Charamut said the alliance does not usually advocate for the use of herbicides, but it’s necessary to stop the spread of hydrilla.
“Just like cancer, there are cancers that are so invasive and damaging that you have to treat it more aggressively,” she said. “There’s science backing to what is happening and if I wasn’t comfortable with it, I wouldn’t be speaking out for people to learn more about this project.”
Social media posts that have been gaining traction claim diquat is being used with no public vote or discussion.
USACE held three public meetings in 2024 about herbicides before starting the treatment plan of five sites.
The herbicides used by the agency have also passed comprehensive EPA risk assessment processes for registration of aquatic use at both the state and federal levels, according to USACE New England District Project Manager Keith Hannon.
The posts also claim diquat is toxic to humans and wildlife.
Hannon said USACE determined that the application of these products will not significantly affect the quality of the human environment.
Diquat was banned for use by the European Union in 2018.
About 20 people protested the use of diquat at the state capitol on Wednesday evening. Most of the people who attended the rally said they learned about the chemical from various online videos and posts.
“I think we the people need to stand together to prove a point,” Joseph Vecchitto, of Meriden, said. “I’m just saying, it doesn’t make sense that we’re so willing to just start spraying stuff because this plant is invasive when we don’t even know what this chemical is going to do to us.”
USACE is planning on expanding the hydrilla management to 12 additional sites this year. The agency is still accepting public comment and seeking permits.
Public comment closes on July 13. To view the public notice or submit a comment, click here.

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