Sonar Treatment

A whole-lake treatment with Sonar (Fluridone) is underway for 2019/2020.  This was determined by the LDAA and LDLD to be the best option for controlling the two most prominent invasive weed species Eurasian Water Milfoil (EWM) and Curly Leaf Pondweed (CLP).   The project will consist of a primary application conducted in June 2019 with a booster application in mid summer and a potential spring 2020 booster. The selected vendor is  Marine Biochemists. The project is financed through a loan which will be repaid with normal LDLD special assessment revenues.  Financing has been secured through the Board of Commissioners of Public Lands (BCPL).  The DNR has approved our request and has issued our permit.  The initial product application was conducted on 6/3/19.  The treatment is working as expected with good control of EWM growth.  This is the first year in many where EWM is not growing above the water surface and getting shredded by boat props.  We need to continue maintaining the Sonar product in-lake level at or above 2 parts per billion (ppb) for as long as we can.  As called for in the plan, we've taken a series of residual measurements and the Sonar product levels have fallen below 2ppb so our vendor conducted booster applications on 8/14/19 & 11/4/19. 

Update 2020

After approval of our 2020 permit, the final booster Sonar application was conducted on 6/9/20.  Although the EWM has successfully been controlled, the CLP has taken advantage of the available nutrients and space in the absence of EWM and is as rampant as the EWM last-year.  Hopefully, the boost of Sonar will slow the CLP spread.  CLP will naturally die off in mid-summer.

As a final step in the project, our vendor has conducted an aquatic plant survey.  The survey report can be found here and has been submitted to the DNR.  The report will inform the DNR as to what abatement remedies will be recommended / permitted next year.

This project has concluded.

Project Plan  |  DNR Fluridone Factsheet  | Project Files


A few dedicated volunteers are monitoring the water quality in the lake and its tributaries through the CLMN and WAV programs.  We measure temperature, clarity, and chlorophyll-A in the lake and dissolved oxygen, clarity, volume, and macroinvertebrates in the tributaries.  These data are uploaded into the SWIMS database and allow us to see how our lake is evolving and target measures to mitigate eutrophication.


Please email if you are interested in learning more.

© 2018-2020 Lake Denoon Lake District  Inc. - Muskego, WI, USA