Lake-wide Milfoil Control

Eurasian watermilfoil came into Candlewood (likely from a boat trailer) in the early 1970's.  It found Candlewood to be a hospitable environment and in a short amount of time it had spread to much of Candlewood's shallower waters along the shoreline.  Not only did it create dense mats of aquatic vegetation, but it out-competed important native vegetation, thereby reducing the biodiversity in Candlewood Lake.  We have been battling milfoil ever since.  

There seems to be little chance of completely eradicating it from Candlewood, but there are options for controlling it.  Historically, a biennial deep winter drawdown (used since the mid-1980's), has been our most effective control method.  Recently, cold winter conditions which are necessary for effectively killing the exposed milfoil have become less reliable, thereby limiting the reliability of the deep draw downs.

The CLA and research partner Western Connecticut State Univerisy embarked on a study to see if the milfoil weevil (a tiny native aquatic insect) could be used as an effective biological control method for Candlewood's milfoil.  The study began in the summer of 2008 and wrapped up five summers later, concluding that while the population of the weevils did increase with the program, they did not increase to the point where they had a visual impact on the milfoil.

Milfoil reaches the surface of the water in Allen's Cove, Sherman during the summer of 2008.  Conditions such as this not only look bad, but can hinder recreation in affected areas.

Candlewood Lake Authority's Sterile Triploid Grass Carp Program

The CLA investivaged numerous lake-wide milfoil control options (including mechanical harvesting, herbicides and sterile grass carp) to look for something that could effectively supplement the winter draw downs.  After speaking with experts in those various control methods, and learning the costs, benefits and drawbacks of each of them, it was decided that using sterile, triploid grass carp, was the best option for Candlewood.


Getting sterile grass carp into Candlewood was no small task.  First the CLA applied for a State of CT DEEP matching grant for the initial stocking.  Additionally, the CLA worked with the CT DEEP and State of CT to revise a regulation requiring all landowners with land under a body of water to approve the stocking.  Also, the CLA and CT DEEP discussed options to meet the requirement of keeping the fish from escaping Candlewood into the Housatonic. 


With funding in place and those two conditions met, the CLA was able to

On June 26, 2015 the Candlewood Lake Authority stocked nearly 4,000 sterile grass carp into Candlewood Lake, to help combat Eurasian watermilfoil.

apply for and receive the permit to stock Candlewood with the sterile carp in the summer of 2015.


To learn all about the sterile grass carp program on Candlewood Lake, click the below button for our grass carp special eNewsletter.

Left to right:  Sterile grass carp, herbicide application, winter drawdowns and mechanical harvesters are all lake-wide milfoil control options.