Aggressive strain of hydrilla at East Twin Lake a growing concern

SALISBURY — The results of an emergency herbicide treatment on Tuesday, Sept. 19 of a four-acre area of East Twin Lake near the marina to control hydrilla’s spread won’t be known for several weeks, but state and lake officials are hopeful it will help keep the highly invasive weed in check. 

The aggressive, non-native plant, discovered in the lake’s waters on June 21 by the Twin Lakes Association’s limnologist, had been sent to the University of Wisconsin-Whitewater for genetic testing and was identified as the Connecticut River variant of hydrilla verticillata, which is far more robust and unlike any hydrilla previously found in North America.

Grant Bogle, president of the Twin Lakes Association (TLA), described the invasive that has taken a toehold in Twin Lakes as a “unique variant that had only been found in the Connecticut River in North America, and now in Twin Lakes.”

Matt Goclowski, supervisory fisheries biologist for the state Department of Energy and Environmental Protection (DEEP) confirmed that East Twin is “the first location in Connecticut where the Connecticut River variant has shown up. It has been in the Connecticut River since 2016 and it’s really exploded everywhere throughout the river.”

TLA officials suspect the plant hitched a ride with an unsuspecting boat owner and may have overwintered in the lake.

 ‘There will be a trade-off’

The threat hydrilla poses not only to the Twin Lakes, but also to other ecosystems, is so severe and urgent that the use of the chemical herbicide, ProcellaCOR, to spot-treat affected areas outweighs the potential collateral damage to some native aquatic plants, according to state and local officials.

“Unfortunately, chemicals are probably the best approach, but we also know there will be a trade-off,” said Bogle. “You can’t harvest it because it breaks up. You can’t put carp in the water, because we are a fishing lake, and it would difficult to manage on anything bigger than a pond.” Unfortunately, he noted, “there is nothing else that seems to work.”  

 “We have been told by the experts that there are no herbicides we can use that are specific enough to kill only the hydrilla,” added TLA board member Russ Conklin, who noted that lake association is working closely with DEEP, a group of lawmakers, state agencies, scientists and leading experts on hydrilla in a unified front to battle the aggressive invasive.

“We now have four Ph.D.’s assisting us,” said Conklin of advisory biologists and scientists, including Northeast Aquatic Research (NEAR), the TLA lead limnologist; SePOR, the herbicide manufacturer; the Connecticut Agricultural Experiment Station (CAES); and the U.S. Army Corp of Engineers, including Benjamin Sperry, lead principal investigator with the Army Corp’s  Engineer Research and Development Center (ERDC).

“There are a lot of people involved. We have a very active Twin Lakes Association that cares a lot about the health of the lakes,” said State Rep. Maria Horn (D-64), who along with Salisbury First Selectman Curtis Rand, requested swift action from the state to treat hydrilla in East Twin Lake.

The first step, said Horn, is urgent: moving fast to combat it. The second step, she said, is to put in place a comprehensive management plan to prevent hydrilla from recurring and spreading to other areas of the Twin Lakes or other bodies of water.

“We have to address the infestation as we find it, and then set up protocols to keep it in check to try to prevent spread.”

Because treatment of hydrilla is very expensive to towns and lake associations, and likely will be an ongoing process for the near future, “we’re sure going to be making the case moving into the next legislative session for additional funding to combat hydrilla,” said Horn. “We need to get ahead of this. It’s going to be an ongoing process and the Twin Lakes will not be alone.”

An expensive undertaking

Battling hydrilla brings with it a hefty price tag. One county in the New York Finger Lakes estimated its management cost at $10 million, according to a study by the Connecticut Center for Economic Analysis at the UConn School of Business.

In addition to damage to the Connecticut River and its tributaries, the spread of hydrilla to lakes and ponds is a major concern, say state biologists.

On Aug. 16, lawmakers and experts from DEEP and CAES gathered in Chester to discuss future plans for controlling hydrilla in Connecticut. At the press conference, Sen. Richard Blumenthal announced that he is looking to secure $25 million from the federal government.

 Management costs for even small hydrilla populations can be high. 

For instance, the cost for hydrilla control with herbicides in Coventry Lake currently exceeds $100,000 annually, according to a CAES Invasive Aquatic Vegetation survey. 

And between 2008 and 2015 Florida spent $66 million trying to fight off the plant.

Bogle estimated that treating hydrilla at East Twin will cost the TLA tens of thousands of dollars just this year but noted that no dollar value can be placed on protecting the lakes.

 “How will it be funded moving forward? I don’t know, but in the end, we are determined to do this right.” 

Threat to sensitive ecosystems

Bogle pointed out that the Twin Lakes drain into the Schenob Brook in Berkshire County,  Massachusetts, which has been identified as a critically sensitive ecosystem for its many rare and endangered plant and animal species. 

“That is a special concern,” the TLA president noted, as is an environmentally sensitive fen in West Twin Lake. “There are all kinds of ecosystems that we are trying to protect, so there is a real urgency here to move with all the scientific folks we can gather.”

The Connecticut River hydrilla grows fast and is more robust than other variants, said the experts.  

“A mature plant, with multiple growing points, can add 20 to 30 inches of plant biomass a day,” according to Conklin. “We had invasives before that were pretty challenging, but they are nothing compared to this.” 

East Twin’s advantage

DEEP’s Goclowski said East Twin has several advantages over the Connecticut River battle with hydrilla because it is not as large a system with flowing water, and so far, the places where the invasive weed has been identified have been fairly limited.

 “It was found early on, and they have a reasonable chance of eradicating it if they jump on it quickly,” said the biologist of the East Twin Lake infestation.

 As for how effective this week’s treatment will be in halting East Twin’s infestation, “We don’t know a lot about how this strain is going to respond to this herbicide, but it will certainly knock it back,” and probably warrants some follow-up spot treatments in the spring, said Goclowski.

“The location of the hydrilla is definitely problematic because that’s the area with the most boat traffic. At DEEP, we are going to be following the situation very closely” in conjunction with the Twin lakes Association and the CAES.

Goclowski further noted that the state’s boating division will be doing outreach to inform the public, particularly boaters, about invasive species, the importance of doing voluntary vessel inspections and tips on avoiding spread from one body of water to another.

Rand said even though he found the DEEP permit process to be “frustratingly slow at times,” he is optimistic that ongoing monitoring and treatment headed by the state with support from the TLA and other environmental groups will result in a favorable outcome.

He noted that regardless of the cost, controlling and eradicating hydrilla in East Twin Lake is the first priority. “We don’t want it to go any further. It’s a terrible thing. We can’t do this every year.” 

Did you know?

Hydrilla, also known as water thyme, is one of the toughest and most economically damaging aquatic plants.

The federally identified noxious weed clogs waterways and slows movement of the water. Its dense, green foliage reduces light penetration and dissolved oxygen levels in the water, hurting fish populations. 

Even the tiniest fragment of the plant can hitch a ride on boats, kayaks, jet skis and even fishing equipment and contaminate other lakes and waterbodies.

Hydrilla also impedes recreation and reduces property values in areas it has infested, according to the Connecticut Agricultural Experiment Station (CAES).

What’s more, hydrilla reproduces in four ways, including sprouting from tiny, broken fragments of its stem. For this reproductive ability, hydrilla was named after Hydra, the regenerating nine-headed serpent in Greek Mythology.