Connecticut plans to spray toxic chemical herbicide into lakes and rivers. Here's context

In late June and early July 2025, a claim (archived) circulated online that authorities in Connecticut would start spraying Diquat, a toxic chemical herbicide, into rivers and lakes after July 4.

Online user Chris Webby, a musician who on his X profile shared a video about the claim that had more than 4,000 views at the time of this writing, said: 

Connecticut is about to poison its own lakes and rivers with a highly toxic chemical called Diquat. And it seems like no one knows about it. It's actually a coordinated plan that they're about to roll out in states all over the country. This particular chemical is banned in Europe and highly toxic to humans and wildlife alike. I've even heard landscapers refer to Diquat as "the nuclear option." The way these s**mbags are getting away with it is by saying it's used to kill an invasive plant species called hydrilla. Which I'm sure it does, along with everything else in the water. And then us, by circumstance.

Webby also started a petition (archived) against the use of Diquat in Connecticut's waterways that had more than 5,700 signatures at the time of this writing.

Another version of the post shared (archived) on X had more than a million views at the time of this writing. The claim also appeared on Facebook (archived), Instagram (archived) and TikTok (archived). Snopes users also searched our site to find out if the claim was true.

It was true that the Connecticut River Hydrilla Control Research and Demonstration Project planned to use Diquat and other herbicides to combat invasive hydrilla in 12 locations across the state (Page 13) starting after July 4, 2025. Diquat is, as some social media claims highlighted, no longer approved for use in the European Union, but as of this writing it still had a valid registration in the U.S. according to the Environmental Protection Agency.

However, the use of Diquat to combat hydrilla was not a new development. The project also used (Page 17) Diquat at two locations in Connecticut in the summer of 2024 for the same purpose. According to the project's draft environmental assessment in 2025, the project considered other methods for control of the invasive hydrilla and found them lacking.

Keith Hannon of the Plan Formulation Branch of the U.S. Army Corps of Engineers (USACE), which manages the hydrilla control project in Connecticut, said via email: 

The USACE's researchers and scientists are dedicated to protecting public health and the environment and only use herbicides that are approved for use in aquatic sites by the U.S. Environmental Protection Agency and the Connecticut Department of Energy and Environmental Protection (CT DEEP). These products have passed comprehensive EPA risk assessment processes for registration of aquatic use at both the state and federal levels.

Hannon added, "Application of any aquatic herbicide product is closely monitored and regulated by both federal and state agencies to ensure that they are safe for humans and the environment."

We also reached out to Webby to ask why he started the petition and await a reply to our query. 

Invasive hydrilla clogs states' waterways

The Connecticut River Hydrilla Control Research and Demonstration Project launched in 2023 to find ways to combat invasive hydrilla, a plant species that, according to the USDA National Invasive Species Information Center, "crowds out native species" and "impedes irrigation and boating." According to USACE, authorities first identified hydrilla in the state near Glastonbury, Connecticut, in 2016; the plant has since spread up and down the Connecticut River.

Section 104 of the River and Harbor Act of 1958 federally authorized USACE to treat hydrilla. The project was federally funded. USACE held public meetings in 2023 and 2024 explaining the scope of the project.

According to project documents (Page 17), USACE first planned to use Diquat to combat hydrilla in Connecticut starting after July 4, 2024.

Hannon said via email that the use of Diquat at two demonstration sites in 2024 had "the desired control effect on hydrilla," though USACE was still collecting data. Hannon said, "In some instances, native aquatic plants growing in the same area were not harmed by the selective herbicide and they increased or expanded their coverage after the hydrilla had been removed. USACE has also not observed any long-term negative changes in water quality following any herbicide treatments."

USACE explained in its 2024 environmental assessment that it had also considered alternative methods to control hydrilla. These methods included mechanically or physically harvesting the plant or introducing species that fed on it. However, USACE wrote in 2025 (Page 7):

Mechanical and physical methods including mechanical harvesting and hand pulling can result in plant fragmentation which can increase hydrilla spread to new areas. Additionally, mechanical harvesting and biological methods, such as grass carp, can lack plant selectivity and can impact native vegetation and wildlife in the area. Various physical methods such as benthic barriers and water drawdowns are not suitable in riverine environments and therefore not considered effective measures.

Webby's petition demanded, among other points, an "immediate halt" to all planned Diquat applications in Connecticut and for authorities to reconsider nontoxic mechanical and biological alternative treatments. The petition recognized the need to manage hydrilla but insisted, "there's surely a better way."

Diquat not without dangers to humans and wildlife

Other states including Massachusetts and Florida also use Diquat to combat hydrilla.

However, the herbicide is considered toxic to humans. One peer-reviewed study from 2025 found that Diquat can severely damage the gut. U.S. Right to Know, a public health research group and newsroom, wrote in an article highlighting that study that Diquat "kills all vegetation that it touches." 

The environmental organization Greenpeace reported in 2024 that Diquat poisonings were on the rise among farmers in Brazil after the country banned paraquat, a similar but more dangerous herbicide, and farmers turned to using Diquat instead.

According to annual reports by America's Poison Centers, a national nonprofit, four people have died in the U.S. from Diquat poisoning since 2020 (the most recent annual report covered 2023). In this time period, the centers registered between 400 and 500 cases of Diquat poisoning each year.

USACE's June 2025 environmental assessment did consider the effects of the use of Diquat and other herbicides on water quality, aquatic vegetation, fish populations and several other areas. The assessment said (Page 35): 

Short-term impacts from the application, such as water quality and herbicide persistence, will be localized and herbicides will be degraded before the sites are considered for retreatment. There may be beneficial cumulative impacts to aquatic vegetation from the proposed action. Future treatment and management of hydrilla may result in increased hydrilla control, in which native aquatic vegetation may reestablish resulting in a more balanced, diverse vegetation community.

USACE also said that Diquat treatment would have "minimal-to-no impact to recreation in the Connecticut River" and that USACE would monitor sites treated with Diquat and other herbicides for up to three years.

In sum, it was true that USACE planned to use the toxic herbicide Diquat to combat hydrilla in the Connecticut River. In fact, 2025 would be the second time USACE used Diquat on hydrilla in Connecticut. 

The project was federally authorized and funded and ran in collaboration with state and tribal entities. USACE held public meetings in 2023 and 2024 explaining the scope of the project. Public documents showed USACE's deliberations both around methodology and potential environmental impact with monitoring of treatment sites included in the project plan.

It was unclear at the time of this writing whether Webby's petition would impact plans to continue Diquat treatment in 2025.