New species of hydrilla found in Middle Pond of Congamond Lakes

SOUTHWICK – While Congamond Lakes have been treated for years to keep the ponds relatively clear of non-native invasive plants, in early October a new plant was discovered, and it is a one-of-kind.

“In 2016, the state of Connecticut realized it had a weird plant growing in the Connecticut River. [It] ended up being a type of hydrilla that is genetically distinct from any other hydrilla in the world,” said Kara Sliwoski, a water resource scientist with the state’s Department of Conservation and Recreation’s Lake and Ponds Division.

“It doesn’t anywhere exist anywhere other than the Connecticut River, Congamond, and a few other Connecticut water bodes as of right now,” she said.

Sliwoski made the announcement during a meeting of the town’s Lake Management Committee in late October.

She was joined by Dominic Meringolo, a project manager with Solitude Lake Management, the firm that has been treating the Congamond for several years to control the growth of the non-native invasive species of curly-leaf pondweed and milfoil.

Hydrilla is an aquatic plant that has earned the illustrious title “world’s worst invasive aquatic plant,” according to the Army Corps of Engineers.

Listed as a federal noxious weed, hydrilla has made its home in just about every conceivable freshwater habitat including rivers, streams, lakes, ponds, marshes, canals, ditches, and reservoirs, according to the corps.

Hydrilla grows very rapidly (it can double its biomass every two weeks in summer) and has no natural predators or diseases to limit its population, increases water temperatures, and affects the diversity and abundance of fish populations, according to the corps.

When the distinctive hydrilla was discovered in the Connecticut River, as first, Sliwoski said no one really knew what to do with it and there was no money to find a solution for controlling it.

Since then, the hydrilla continued to expand and now there is about 1,000 acres of it on the Connecticut River with its northern most infestation where the river passes by Agawam in the area of Six Flags New England.

“If you are right next to (the rollercoaster) Superman and in the river, it’s there,” Sliwoski said.

And during the summer, she said, the Connecticut Agricultural Experimental Station “accidentally” discovered it in several other small bodies of water.

She said while the CAES was researching the possible areas of infestation, they found a bass tournament schedule from 2020 that had all the bodies of water where the hydrilla was found, which included Congamond.

She said it was theorized that boats or trailers carried the hydrilla fragments from other water sources where the new hydrilla was growing.

At that point, the CAES researchers contacted Sliwoski and told her they believed there might be an infestation in Congamond.

The researchers, acknowledging they were not in their jurisdiction said Sliwoski, checked the two public boat ramps on the Lakes.

“And sure enough, they found it,” she said.

It was found just along the shoreline at the public ramp on the Middle Pond, with a smaller infestation across the pond from the ramp, she said.

Usually, Sliwoski and Meringolo said, the hydrillas that typically infest bodies of water are very difficult to control.

Meringolo went through a list of aquatic herbicides and other treatments that have been tried to control the infestations. Most, he said, had an insignificant effect.

However, the Connecticut River hydrilla found in Congamond is different in a way that might make it easier to control; it doesn’t have a “tuber,” which imbeds itself in the pond bottom, both said.

With no tuber to reproduce as the waters warm, a topical herbicide could possibly kill off the leafy portion of the genetically unique hydrilla.

It seems to spread primarily through “budlike nodules on the plant’s stem that can break off and root where they drop,” according to Greg Bugbee, a scientist with the CAES in an article on the new hydrilla in www.waterline.com.

Sliwoski said the corps has allocated $6 million for a pilot herbicide treatment project this summer.

According to the corps’ website, the project will investigate the unique hydrilla’s growth patterns, water exchange dynamics in the Connecticut River, and evaluate herbicide efficacy in laboratory conditions in 2023 to guide operational scale field demonstrations of herbicide efficacy in 2024.

The federal agency will be running the pilot programs along seven areas of the Connecticut River this summer, according to its website.

The closest bodies of water to Congamond Lakes that is part of the pilot is Keeny Cove, which is just outside of the town of Wethersfield, Connecticut.

Sliwoski said that last summer Keeny Cove was treated with an herbicide called Diquat and early indications were that the infestation had cleared.

Diquat is already used in on Congamond Lakes to control curly-leaf and milfoil, said Richard Grannells, the chair of the LMC.

“We’re covered to use Diquat,” Grannells said during the meeting.

He asked Sliwoski if it was too late in the season to treat infestation.

Sliwoski said that in September it may have been practical, but in October it was too late.

Solitude’s Meringolo pointed out that treating milfoil and curly-leaf with herbicides in mid-May when it is growing.

However, the new hydrilla tends to grow late June and early July.

Grannells asked Meringolo how much the additional treatment might cost, suggesting it costing $4,000 to $5,000.

Meringolo said, however, it was too soon to make an estimate.

The next step, Grannells said, was to have the ponds surveyed and after the first treatment, surveyed again to determine if it worked, which would happen this summer.