Lyme ― An airboat more commonly associated with the Florida Everglades was in Selden Cove on Tuesday as it skimmed over the monstrous mass of hydrilla lurking just below the surface.

The boat, operated by Marc Bellaud of SOLitude Lake Management, was outfitted with hoses pumping a fluorescent red dye into the water in a test run for the application of aquatic weed killer next year.

A team of scientists from the U.S. Army Corps of Engineers and Connecticut Agricultural Experiment Station is working to better understand the unique attributes of a hydrilla species unlike any other seen in the United States.

Selden Road resident Joe Standart was on his dock Tuesday morning watching the airboat’s red wake as it traveled across the cove. He said he was encouraged by the team’s efforts to figure out the most effective and safest way to apply herbicide. It seemed for a while as if there were no solution to the problem that “just all of a sudden appeared” a few years ago, according to Standart.

The unique variant of the herb now found throughout the Connecticut River has long been known as the world’s worst aquatic invasive species. But this version is thought to be even more resilient than its domestic predecessors.

The tracer dye – just under a gallon of it diluted in a large tank of cove water before getting injected into the weed-choked inlet – was visible in the wake of the 5-foot propeller and V8 engine. The solution was harder to see in the main body of water already rendered cloudy by months of floods.

Bellaud finished the application just after 10 a.m. and pulled up to the dock. That’s when two scientists with the Army Corps set out on a small motorboat to take their first post-application measurements in an effort to document how long the dye would stay in the water.

Bellaud said the dye mimics the flow of herbicide. The length of time the colorant remains in the water will help scientists determine the type of weed killer best suited for the area and how much of it should be used.

The Army Corps has said the dye has no significant effects on aquatic organisms and has been proven by its Engineer Research and Development Center to be safe for use.

Jeremiah Foley IV, an assistant agricultural scientist with the agricultural experiment station, said the state’s uniquely resilient hydrilla plant was first identified in 2016 and is now approaching a period of exponential growth if something isn’t done to stop the spread.

“It’s here, it’s nasty and Connecticut is ground zero,” he said. “We knew it was going to happen, and now we have the data to show it.”

Selden Cove is one of seven areas within the Connecticut River slated for herbicide application next year as part of the program, according to Foley. The partnership between the Army Corps of Engineers and agricultural experiment station also includes the Lower Connecticut River Valley Council of Governments.

Foley said genetic evidence shows the strain of hydrilla clogging Connecticut waterways likely came from China as part of the aquarium hobby market that prizes easy-to-grow plants for fish bowls and tanks. The problem comes when people who no longer want to keep their pet fish dump them in the river with the contents of the aquarium.

The particularly robust, cold-tolerant herb breaks off easily into new plants that can regrow the next year.

“So those attributes that are ideal for an aquarium environment are not ideal for ecology,” he said.

The infestation now covers over 1,000 acres of the Connecticut River and has been identified in Amos Lake in Preston and Twin Lakes in Salisbury, where scientists believe the plant was tracked in on boats and trailers.

Foley, whose background is in the study of insects, said efforts to manage hydrilla included unsuccessful attempts in Florida to use weevils and flies to help control the spread of the plants.

But he emphasized the type of hydrilla in Connecticut is genetically distinct from hydrilla found in Florida and other states. One thing he would like to study is the effect of those insects on this unique strain.

“Oftentimes, if an insect chews on the plant just enough, it becomes more susceptible to herbicide and then you can use less herbicide,” he said.

Another way to manage hydrilla involves mats called benthic barriers that are laid at the bottom of the water for two months to prevent the growth of hydrilla. He said it’s been successful in smaller areas to keep water clear for swimmers.

The team is “keeping everything on the table” when it comes to a management plan, according to Foley.

“We’re not looking for one method over another; we’re trying to understand each one independently and ultimately try to marry them together for some sort of holistic integrated pest management strategy,” he said.

But the scientist acknowledged the immediate plan revolves around herbicide use.

“At this scale, it’s ecologically and economically unfeasible to do anything else,” he said. “It’s over a thousand acres of infestation of the river, which is an ungodly amount.”

e.regan@theday.com