Aquatic Hitchhikers

Eurasian Watermilfoil

Starry Stonewort

Zebra Mussels

Curly Leaf Pondweed
Aquatic Invasive Species
In 2009 while doing shoreline studies, the DNR discovered Eurasian Watermilfoil (EWM) in the East Basin not far from the public landing.  A 4.5 acre area was chemically treated.  The following year, volunteers with scuba gear, kayaks, and boats searched the water of the East Basin and walkers searched the shoreline looking for signs that the EWM had spread.  
Two small patches were found in 2012 which were treated.  As of 2014 there had not been a reoccurrence of EWM in these areas.
In August, 2014, three new areas totaling 11 acres were found and treated.  LWA will continue to be diligent against the spread of all Aquatic Invasive Species. 
As of August 2016  reports  show no new AIS plant sightings. 
We have had two summers now since we treated for Eurasian Watermilfoil.  Last year there  were numerous hours of LWA folks surveying for EWM and the Association hired a professional to survey the East Basin.  We have had two years when no EWM was found (nor any other invasive species).

AIS Decon Stations-01.png
LWA PLM Treatment.jpeg

The treated area is clean, and the treatment looks like it was extremely effective.  The chemicalls were quite selective.  Some Northern milfoil survived, but it looked like it was knock down and is regenerating.  What I call cabbage looked good and is on the surface.  The EWM was gone, dead and you could make it out, or just a brown brittle stalks was left.   Other plants were pretty much unaffected.   

July 20, 2019


As of report at the Annual Meeting on August 10th, the treatment of the area was very successful.  

A full survey will be done on the lake within the next couple months to check to make sure there are no other areas that are infested. 

The mass of weeds in the East basin are not invasive.  At this time the DNR has no plans to manage the masses.

Our approach to AIS is not just surveying and treating for EWM.  

Great strides have been made in boat inspections thanks to those who have worked diligently to coordinate inspections in conjunction with our neighbors and the township. These efforts are key in keeping out other invasive species such as zebra mussels, curly leaf pondweed, and starry stonework and many others.


Education is important.  Learning to identify and prevent AIS.  There are signs on all major roads to the lake as a reminder to inspect your boat before using numerous public and private launches on the lake.

Remember to drain, clean, dry your watercraft!     



Zebra Mussel

Early Detection

Installing an early detection device on your dock is one of the easiest ways to help against the infestation of zebra mussels.  It hangs from the dock on a rope.  The device should be placed about one foot from the bottom of the lake and checked monthly. The baby zebra mussels - Veligers attach themselves to it causing the pipe to feel rough.  

Contact the DNR or lake association if any detection occurs on the device.

If you have an interest in the detection device -

 Contact Bob Holman

 Lake Washburn Association

 Gary Langer, RALALA

or any other

Crooked Lake Township 

AIS committee  member.



As you drive through the Central Lakes Region of Minnesota, you will see many signs concerning Aquatic Invasive Species (AIS) posted in many cities and along highways, especially at marinas and public landings.  There is a high degree of AIS awareness in the lakes region and a strong effort to restrict the spread of the AIS contamination to other lakes.

Many of these signs will suggest that you “Decontaminate” your boat or watercraft. That request does not mean to imply that your boat may be dirty and need to get it washed, it suggests your boat needs to go through a specialized decontamination process designed to remove zebra mussels and Eurasian watermilfoil. 

Adult zebra mussels and mussel larvae called veligers are very tenacious creatures and can attach themselves firmly to any solid surface such as boats, dock, lifts and anchors. They are very difficult to kill and very difficult to see and remove as well. The primary method of AIS contamination is by being transported into the lake by a contaminated boat, dock or lift.

The adult zebra mussel and Eurasian watermilfoil are relatively easy to see but may be difficult to remove from your boat, trailer or other equipment. When the water temperature reaches 54 degrees (F) or higher, the zebra mussels are able to reproduce releasing millions of veligers into the lake. The veliger larvae are microscopic and cannot be seen with the naked eye. You could not see them even if you looked for them. They drift on the surface of the water with the wind and the current looking to attach to a solid surface; a boat or dock being an ideal target. They can attach themselves to your boat and then the boat carries them wherever you go and contaminate other lakes where your boat is launched.

Attached to a boat, a simple car wash with a garden hose is not going to kill them or remove them from your boat. The Watercraft Decontamination Process uses very hot water (120 degrees to 140 degrees (F)) under pressure to blast the veligers, vegetation and adult zebra mussels from your boat. The DNR states that it takes at least 10 seconds of pressurized hot water exposure to kill off the zebra mussels.

The Watercraft Decontamination Process can be dangerous using pressurized hot water and requires specialized training and equipment. The Level 2 Inspectors that operate the Decontamination Stations are extensively trained by the DNR. There are many unique hiding places that mussels or veligers can find to hide on a boat, in an engine, on a trailer and on all the other equipment used in watercraft. It takes specialized training to find them and to clean them out. Decontamination is not a do-it-yourself project.

The $10M the Minnesota Legislature voted to distribute to some counties to fight AIS funds the Level 1 Inspectors who inspect your boat at the public landing for visual evidence of AIS and for the Level 2 Inspectors that operate Decontamination Stations. Cass County administers the entire Level 1 and Level 2 Inspector program in Crooked Lake Township. They purchased the decontamination unit and equipment needed for the Decontamination Process found near the Outing Canister Station behind the Town Hall. If your boat has been in other lakes, especially lakes with known AIS contamination, you definitely need to get your boat decontaminated. You do not need to wait for an inspector for a recommendation, you can get your boat decontaminated anytime the station is open – a free service to protect our waters.

Eurasian Watermilfoil Search & Delineation Survey

Washburn Lake (#11-0059)

Cass County, MN

Surveyed: September 8, 2017

Click on PDF to read report -