Invasive Aquatic Species Continue to Do What They Do Best

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Milfoil, or Myriophyllum spicatum, has been steadily taking over Connecticut lakes for years. Photo courtesy of moosepondassociation.org.
Milfoil, or Myriophyllum spicatum, has been steadily taking over Connecticut lakes for years. Photo courtesy of moosepondassociation.org.
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There’s nothing like spending a warm summer afternoon at a lake that sits in your own backyard. When it’s time to cool off, you anxiously approach the shore and wade into the cool water. To your dismay, you feel a familiar brush against your legs, reminding you that that pesky water weed, milfoil, is here for the summer again.

 

For years, milfoil has become an extreme annoyance for numerous bodies of water in Connecticut.

 

According to the Unites Stated Department of Agriculture (USDA) National Agricultural Library, milfoil, or Myriophyllum spicatum, is native to Europe, Asia, and North Africa. It was first seen in the United States between the 1880s and 1940s.

 

The Candlewood Lake Authority states on their website that milfoil arrived to the lake, which spans through Brookfield, New Fairfield, Danbury, Sherman, and New Milford, in the late 1970s. The plant can grow up to 15 feet in the water, and when fragments break off, either by itself or by boats or people, the fragments form roots and regenerate.

 

Tim Watko, a Candlewood Lake resident of 13 years, has experienced the frustration caused by milfoil. He and his wife work tirelessly all summer in attempts to control the milfoil growth on their shoreline property.

 

“We have to literally rake this stuff up,” said Watko in an interview. “I wish there was an easy solution.”

 

Zebra mussels on the bottom of a boat. Photo courtesy of marinedocklift.com.

Another invasive species is mucking up Candlewood: a small population of zebra mussels, which could have been pumped into the lake from the Housatonic River. Milfoil and the zebra mussels are both most commonly transported from motors and propellers of boats travelling from other bodies of water. However, at Candlewood Lake, the prospect of eradicating zebra mussels has taken a back burner to the milfoil issue .

 

“This sort of swamps any other problems,” said Watko.

 

The Candlewood Lake Authority does make attempts to control milfoil by drawing down the lake before winter, which kills the parts of the plant left exposed. The more the lake is drained, the less severe the plant’s growth is the following summer.

 

The Lake Authority has also purchased Eurasian watermilfoil weevils, small beetles that eat mostly milfoil. At the larval stage, they burrow into the stem and rob the milfoil of its nutrients and kills it. Unfortunately, they do not contribute a significant measure of milfoil control, according to the Authority.

 

Some additional control methods used by the Candlewood Lake Authority include weed cutters and benthic barriers.

 

Weed cutters are sharp blades that slice milfoil but do not remove its roots. This acts as only a temporary fix.

 

Benthic barriers are large mats that are placed on the floor of the lake to prevent vegetation from growing. It blocks sunlight and allows gases from the vegetation’s decompostion to pass through.

 

Other methods used to control milfoil include suction harvesting and mechanical harvesting: the plant is suctioned by a tube in suction harvesting, the most preferred method, and mechanical harvesting involves a large, submerged machine that slices the top few feet of the plants, acting much like a lawn mower.

 

Grass carp, a fish that only eats plants, has been introduced into Candlewood in hopes that they will eat a significant amount of the milfoil. The carp are bred to be sterile to avoid an overproduction of the fish, and a permit from the Connecticut Department of Energy and Environmental Protection (DEEP) is required in order to introduce them into a body of water in-state.

 

 

One of the most effective control methods for Taunton Lake has been using herbicides made specifically for milfoil eradication; two years ago, herbicide was applied in Taunton and killed approximately 80 percent of the milfoil population. There was about 24 acres of milfoil in Taunton Lake prior to the herbicide application, but this only proved to be a short-term solution.

 

 

There was about 24 acres of milfoil in Taunton Lake prior to the herbicide application, but this only proved to be a short-term solution.

 

Permits are also required to treat milfoil with chemicals and herbicides. Herbicides either kill the plants they come in contact with or are applied systemically to atrophy the plant’s roots.

 

Kevin Kohn, President of the Taunton Lake Association in Newtown and a resident of the lake for 33 years, shares the same frustration with milfoil as Watko.

 

“There’s no easy solution,” said Kohn in a phone interview.

 

One of the most effective control methods for Taunton Lake, a significantly smaller body of water than Candlewood, has been using herbicides made specifically for milfoil eradication; two years ago, herbicide was applied in Taunton and killed approximately 80 percent of the milfoil population.

 

There was about 24 acres of milfoil in Taunton Lake prior to the herbicide application, but this only proved to be a short-term solution.

 

“Right now we’re at the same exact spot we were two years ago,” Kohn said.

 

In October, the Taunton Lake Association plans on introducing sterile grass carp into the lake.

 

“We are hopeful and optimistic that it could be a long-term solution,” Kohn explained.

 

Milfoil has populated the shorelines around the entire perimeter of both Candlewood and Taunton. Candlewood Lake is 5,420 acres square and Taunton Lake covers 126 acres.

 

DEEP’s Nuisance Aquatic Vegetation Management guidebook offers useful tips and guidelines for those affected by invasive plant species.

 

“When these plants become overabundant, they can lower the recreational and aesthetic qualities in a body of water, and also alter some of the natural qualities such as fish community structure,” the guidebook states. “[...]Before starting to control aquatic vegetation, pond or lake owners and  managers need to assess the uses of  the water, and develop a realistic goal  for the water body. At this point control measures should be evaluated. For example, very few ponds in Connecticut  are capable of supporting trout on a long term basis. Therefore, a  management plan for fly fishing in one’s backyard pond may be unrealistic. Similarly, swimming in clear water with a sandy bottom can be difficult to achieve, and may require continuing treatment to be possible. Ponds that attract wildlife however, are much easier to achieve.”

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