Invasive Species Management Projects

Flowering Rush

The Pelican River Watershed District has been working with Dr. John Madsen and Dr. Grey Turnage from Mississippi State to monitor the effectiveness of Flowering Rush control and potential eradication with the use of carefully applied herbicides.  Since the beginning of the project in 2005, large reductions in Flowing Rush beds have been observed throughout the District.

2016 Final Report

The Research Study was completed in 2017 and we are now in the adaptive management stage.  District staff conducts surveys on the lakes each year to determine Flowering Rush treatment areas.  Based on plant densities, some areas receive only one treatment and some require two treatments.  These treatments are ideally applied in late June and late July.


Flowering Rush regression photos can be seen below.

Deadshot Bay

Busker's Beach West


Curly-Leaf pondweed

Historically, the PRWD obtained permits from the MN DNR each year to harvest curly-leaf pondweed to help control the population and density.  No eradication techniques had been found, however, harvesting allowed for recreational activities to continue.  However, in 2016, the district began chemical treatment on the most dense patches on Lakes Detroit, Curfman, Sallie and Melissa.  The chemical treatment was very successful and was therefore continued in 2017.  

In 2018, ice-off was later than usual and in mid-May unseasonably high temperatures were experienced.  This made conducting early season CLP treatment a challenge.  Fortunately, the District was able to delineate the CLP and treat before the water temperatures became too warm.  Upon surveying the treatment areas in Detroit, Sallie, Melissa and Muskrat, it was found that of the 95 points surveyed, only 10 were found that had any amount of CLP growth, and these plants suffered significant damage.  There is a location on the southwest side of Lake Sallie where growth was still detected.  Staff will review alternative treatment options for this area for the future.


Zebra Mussels

Zebra mussels were first confirmed in Lake Melissa in 2014 and were found in Lake Sallie and Detroit Lake in 2016.  There were no new infestations in 2017, however, Floyd Lake was designated as infested in 2018.

Early in 2018, District staff contacted the University of Minnesota AIS research staff to develop protocols to effectively monitor and observe changes in lake ecology due to zebra mussel infestations.  It was determined zooplankton studies would be the best indicator for changes in algae composition and distribution shifts (nutrient levels) and food web changes which can affect fisheries.  A program similar to current MN DNR monitoring studies was recommended and implemented.    

At multiple locations on Sallie, Melissa and Detroit, PRWD coordinates zooplankton testing with the DNR and added phytoplnakton composition and biomass sampling, per the U of M research recommendation.  PRWD ships samples to MN DNR,  who performs the analysis and drafts final reports.

Decontamination of boats and equipment is critical in stopping the spread of the invasive mussels.  Equipment should be left out over the winter to be sure there are no surviving mussels if you plan to sell or move equipment to a different lake.

The image below is from a District lake in 2018 and shows how zebra mussels cover branches and plants in a lake system.




MAISRC comes to Detroit Lakes

PRWD staff was instrumental in organizing a seminar held on June 8, 2018 at M State in Detroit Lakes which featured University of Minnesota AIS Research Center (MAISRC) staff.  Director Nick Phelps lead off with an overview of current projects.  Other researchers discussed zebra mussels, starry stonewort, the AIS Detectors and Trackers program, as well as  current research on the effects of spiny water fleas and zebra mussels in Minnesota's ten largest walleye producing lakes.

The event was also sponsored by Becker County COLA, Hubbard County COLA, Ottertail AIS Task Force, as well as County AIS Coordinators from Becker and Ottertail County.  Approximately 125 people were in attendance along with Senator Kent Eken and Representative Steve Green.  Attendees were very appreciative that they could hear directly from researcher without having to travel to the metro area. 

MAISRC Crowd.jpg 

Above:  Attendees included many area lake association members, staff from MN DNR, MPCA and local government officials.

Below:  Director Nick Phelps gives insight as to how research is conducted.

MAISRC Phelps.jpg

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PRWD in the News

PRWD/MN DNR Zebra Mussel impact study

MPR News Story on PRWD Flowering Rush Project

Dan Gunderson, MPR News, visited Lake Sallie with Brent Alcott to discuss the success of the…

MnDNR begins ZM pilot project treatment

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Recent Water Levels
Detroit 1333.9 ft
Last Updated: 10/10/2018
Floyd(s) 1354.6 ft
Last Updated: 10/10/2018

Melissa 1328.2 ft
Last Updated: 10/10/2018
Sallie 1330.2 ft
Last Updated: 9/28/2018

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