That’s the sound of an airboat, typically associated with the Florida Everglades, but it's now helping to tackle an invasive problem on the Connecticut River. The airboat is part of an ongoing study to track the spread of Hydrilla, a water plant that has been wreaking havoc on the river for years.
Keith Hannon, from the New England District of the U.S. Army Corps of Engineers, is managing the project. Since the early 1900s, the Corps has overseen the nation's navigable waterways, including the Connecticut River.
Hannon explains that the airboat is being used to add a tracer dye to the water—not to track Hydrilla directly, but to understand better the river's flow, which will help guide the application of herbicides.
“We want the dye to mimic the water flow in the river during Hydrilla’s peak growing season," Hannon said. "When it grows thick, Hydrilla can actually affect the water flow, so we need to recreate those conditions to target the herbicide effectively.”
Dr. Jeremiah Foley, a scientist with the Office of Aquatic Invasive Species at the Connecticut Agricultural Experiment Station, is also working on the Hydrilla project. He explains that Connecticut’s Hydrilla is unique because of the way it spreads.
“The Connecticut River Hydrilla produces a massive number of turions—seeds that fall off or break off the plant, especially during manual removal," Foley said. "These fragments can float downstream and start new populations, making it hard to control. It’s named after the Hydra from Greek mythology because, like the myth, when you remove one part, two more can grow.”
This is a major challenge for researchers. But Foley said they are starting to make headway. A dye study followed by herbicide treatments in five river locations has yielded positive results.
“We applied herbicides in 2024, based on the dye data from 2023. The results have been great—there’s almost no Hydrilla left at the treatment sites, while native plants are thriving. This shows that herbicide treatments can be both selective and effective,” Foley said.
The third agency involved in the project is the Lower Connecticut River Valley Council of Governments (LCRVCG), which first raised the alarm about Hydrilla after property owners and river residents started noticing its spread.
Margot Burns, Senior Environmental Planner at LCRVCG, said while they're encouraged by the success of the herbicide treatments, there's still a long way to go.
“The lower coves and shallows are heavily infested. Hydrilla is basically taking over in those areas,” Burns said.
However, as Burns points out, even with herbicide success, the human element remains critical. Education is key to preventing further spread.
“We need to encourage people to ‘Clean, Drain, Dry’ their boats. Everyone needs to work together to prevent further spread,” Burns said.
Burns said that as long as funding allows, the LCRVCG will continue posting signs at public boat ramps and working with private ramp owners to keep people informed about Hydrilla and how to prevent its spread.
Foley is optimistic but cautious about the future. He says they will never be able to eradicate Hydrilla from the Connecticut River fully. Instead, ongoing monitoring and a combination of treatments will be needed to manage it long-term.
However, one concern remains: the possibility of Connecticut’s Hydrilla cross-pollinating with other strains of the plant.
“There’s concern that Hydrilla could crossbreed, potentially creating a new genotype. But that’s something we’ll have to study further,” Foley said.
For now, the battle to reclaim the Connecticut River from Hydrilla is ongoing, but scientists are making significant progress.
