It’s in CT and called ‘the most noxious, invasive species known to man.’ It’s spreading.

The U.S. senator headlined what amounted to a pep rally for environmentalists in Hartford to support eradication of the invasive, aquatic superweed hydrilla, which threatens to choke the Connecticut River and the $1 billion it generates annually in recreation and other economic activity.

U.S. Sen. Richard Blumenthal called hydrilla, which has exploded along the lower river over the last decade “the most noxious, invasive species known to man” and announced he has secured another $5 million to support a developing plan by state and federal agencies to begin fighting it with targeted herbicide treatments next month.

Business and environmental advocates have become concerned that unique species of hydrilla expanding exponentially along the lower river threatens a half a century progress that changed it from what former Old Saybrook resident Katherine Hepburn once described as “the world’s most beautifully landscaped cesspool” to what the Nature Conservancy now calls “one of the world’s last great places.”

Invasive plants choke CT waterways. The state will fund groups with proposals to reduce the threat.

Marina owners are paying to have channels cleared of the thick mats of weed that bind boat propellers and stall engines. Kayakers can’t penetrate it, swimmers won’t swim in it and fishermen have given up on choice spots in coves and creeks because it is impossible to drop a hook through it. Hydrilla threatens to dam shallow tributaries such as the Mattabesset in Middletown, turning them into giant mosquito breeding grounds. Owners of million dollar waterfront homes look out over mats of weed and tax collectors are worrying about property values.

A noxious weed threatens the CT River. Students created a device to join effort to eradicate it.

Nationally known experts like Gregory Bugbee, who leads the state Office of Aquatic Invasive Species within the Connecticut Agricultural Experiment Station, have said the local hydrilla is so robustly dominant that it alters the river ecosystem to suit itself, driving off or killing native plants and fish. There is concern it could nurture an algae-like cyanobacteria fatal to big birds like bald eagles and osprey that are repopulating the river.

The officially named “Connecticut River Hydrilla” has what Blumenthal called the “dubious distinction” of being a genetically distinct species from the invasive weed that has plagued the southeastern US for decades. It is believed to have originated somewhere in Eurasia as decorative vegetation for aquariums. Bugbee and others believe it got into the river when families dumped their kids’ aquaria

Blumenthal said the $5 million he procured will be added to money already budgeted for the next stage of an anti-hydrilla campaign by the U.S. Army Corps of Engineers.

Hydrilla wasn’t even heard of in the Connecticut River until 2016, when it was first detected in Keeney Cove in Glastonbury during a field trip called a bio blitz by a group of volunteer scientists and river enthusiasts. Bugbee and his colleagues then spent three years plotting its explosive growth. It now covers more than 1,000 acres between Essex and Agawam, Mass.

Based on charting by the state scientists, the Army Corps last year poured harmless dye into the river at various locations to plot flow directions and speeds. Based on those results, the corps plans to introduce a state and federally approved herbicide into the river at six locations this summer and study its effect on the weed.

Much of the discussion outside the boathouse at Hartford’s Riverside Park Wednesday was directed at anglers and other boat owners who trail boats between the river and state lakes and ponds. Tiny fragments of hydrilla that attach to trailers and hulls can survive days out of water and are believed, just over the last year,  to have transplanted the weed to seven state lakes and ponds.

Bugbee said it was first detected in East Twin Lake in Salisbury a year ago. It was discovered Tuesday in Bashan Lake in East Haddam. Blumenthal and others urged boat owners to wash down any boat pulled out of any state body of water before relaunch. Bugbee said warning signs are being placed at all boat launches in the state.