AIS ( Aquatic Invasive Species) (sometimes called exotic, nonindigenous or non-native) are aquatic organisms that invade ecosystems beyond their natural, historic range. Their presence may harm native ecosystems or commercial, agricultural, or recreational activities dependent on these ecosystems.  Listed below is information on two AIS that have been found in Long Lake, Curly Leaf Pondweed and Yellow Flag Iris, and one which has invaded a nearby lake, Zebra Mussels.  If you have any questions concerning the removal/disposal procedures for AIS, feel free to contact Lisa Burns, Washburn County Land & Water Conservation/Aquatic Invasive Species specialist.


Curly Leaf Pondweed (CLP) is an invasive aquatic plant which has been present in Long Lake for some years.  Until recently it did not form significant beds thick enough to interfere with navigation; a 2004 survey by UW Stevens Point reported that its presence was not yet significant, but predicted that would likely change.

That prediction was, unfortunately, accurate.  Commencing in 2014 LLPA has annually mapped CLP with a mapping GPS unit along the entire shoreline and other shallow areas.  Each year’s results are printed onto a map, with each year being color coded so year to year changes are apparent, and it is apparent that CLP has spread.  In 2017 in particular it was found far from earlier locations.   For reasons which are unclear, but possibly related to the late ice out, 2018 was a “down” year for CLP; there wasn’t enough growth to successfully map.  Anecdotal evidence suggests this was true of other lakes in the area as well.  It had returned in 2019 and again in 2020, but subjectively appeared less dense than in 2017 and did not appear to have extended its range.  We thus elected not to clutter the maps with additional colored dots which wound be of little significance. Inspections will continue to be made, and if expansion becomes evident the maps will be updated.

The 16 maps generated following the 2017 survey are at the link below.  The first page is a whole lake overview.  It is followed by more detailed maps, commencing at the Long Lake Road culverts at the far north end and working down the lake, around Christiana Point and up to the Elvers Road culvert at Lower Mud Lake.

CLP Maps

The problem with CLP is that, like most invasives, it can crowd out native species and form dense mats at and near the surface, impeding navigation and even restricting the ability of fish to swim freely.  This results because it starts growing under the ice, giving it a head start on most native plants.  The positive in this is that it also dies out early, usually by mid-July.

Efforts to control CLP by use of herbicides has not proven effective in the long term.  There was a school of thought that chemical treatment of a given area for three consecutive years would result in long term control.   LLPA did attempt this at some beds just downstream of the Narrows.  Control was effective during the years of application, but after three years there were no lasting effects.  Annual treatment of large areas would be very expensive..

LLPA is exploring possible options, and will continue annual mapping to monitor further expansion. For now, the best solution for individual landowners is to manually pull the plants from around docks and lifts and dispose of them in the trash.  This should be done as early in the summer as possible, as the mature plants form seed pods (called “turions”) which, when the plant is pulled, fall to the bottom where they may sprout the following year or even several years hence.


 Yellow Flag Iris is a relative newcomer to Long Lake.  Aside from color, it resembles the familiar native Blue Flag Iris, and is equally appealing in appearance.  But there the similarities end.  Growing along the shoreline, it expands quickly and can form dense stands which crowd out aquatic plants such as cattails and native irises.  Its root system also forms dense mats which inhibit the growth of other plants.  It expands by spread of its rhizome root system and also produces floating seed pods.

While at this time it is present only in small clumps in Long Lake, mostly along the developed shoreline between the Narrows and Crows’ Nest, it appeared to be present in more locations in 2017 than in prior years.  Small clumps can be controlled by digging up the plant, but care must be taken to remove all rhizomes, as they can persist for more than ten years in soil.  Be sure to dispose of them in the trash, not a composter, for even a dried rhizome can survive for over three months.  Gloves should be worn while handling because the sap can cause skin irritation to sensitive persons.  All parts of the plant are toxic, especially the rhizomes.


Zebra Mussels are an invasive species which has not been found in Long Lake, but it has invaded the area.  Recent LLPA newsletters have reported on their appearance in nearby Big McKenzie Lake, which lies partly within Washburn County.

Zebra Mussels are comparatively small, usually about the size of a fingernail.  Their strength, and their danger, is in their sheer numbers.  They have the potential to be extremely damaging largely because they are incredibly prolific. A single female can lay up to one million eggs per spawning season, and even at a 
survival rate of only two to five percent the
 population can mushroom. They tend 
to attach to hard surfaces, and when
 the population grows enough
 they clog water intakes and 
boat motors, attach themselves
to native mussels, and shells 
of the dead wash ashore in
 great masses, cutting the feet
 of anyone attempting to wade
 there. Perhaps most significantly 
they out-compete native species 
for food by voraciously filter feeding on organisms at the base of the food web.

In our area Zebra Mussels have few natural enemies, and hence their rapid reproduction. Carp are known to feed on them, but introduction of carp for that purpose would be a definite leap from the frying pan to the fire. Some success has been reported treating infested water with a form of dead bacteria which disrupt their digestive system, as well as with a copper based product, but those techniques are far from proven yet, and can be extremely expensive.  Research on how best to control them is continuing.

The best defense against them is to keep them out of the lake in the first place. That can be difficult because of how they spread.  Since they are small one or two attached to a boat hull or outboard lower unit may not be obvious absent careful inspection.  They can live out of water for several days, especially in cool weather.  Even more significantly, their free-floating larva start out as being microscopic, undetectable by the human eye. That is why it is so important to follow the rules about not transporting water from lake to lake. Visual inspection alone is not enough. Drain everything.

LLPA has continued Clean Boats Clean Water inspections at major landings. Additionally, because early detection gives at least some hope of control we have built Plexiglas devices known as collector plates and suspended them from docks at landings, the idea being that if they are present they will attach. Thus far all inspections have been negative, but only continual vigilance and adherence to the no water transport rules by every boater can keep them at bay.

New decontamination station

Most recently LLPA and the Long Lake Chamber of Commerce have jointly erected decontamination stations at the four major public landings.  (See Decontamination FAQ Sheet.)  Each station consists of a 4×8’ sign with a cleaning brush, weed removal hook, goggles and a one gallon sprayer containing a mild bleach solution.  The bleach solution is targeted at larva of Zebra Mussels.  Two of the stations were supplied by the Washburn County Land and Water Conservation Department, aided by a WDNR grant, and two were purchased by LLPA and the Chamber.

The bleach solution is for spraying all portions of boat, motor and trailer exposed to water.  Directions are plainly set forth on the sign.  Since the active ingredients of the bleach break down chemically in a day or two, volunteers are needed to replenish it during the boating season; anyone willing to help should contact any LLPA board member.

It should be noted an Ordinance enacted by Washburn County in 2018 provides that if a decontamination station is available at a landing, it shall be used in accordance with the posted instructions.  We all appreciate that this adds a little time unloading and loading, but if that helps keep invasives, especially Zebra Mussels, out of Long Lake, it is worth the effort many times over.

For more information on these and other invasive species known to exist in Washburn County, go to: