Eurasian watermilfoil equals big bucks

What is Eurasian watermilfoil and how does it equal dollars to everyone? Eurasian watermilfoil (EWM) is an invasive non-native aquatic plant that is classified as a noxious weed. It affects fish and wildlife populations, makes recreational use difficult, if not impossible, and can reduce property values, all resulting in dollars lost or spent. The control of this aquatic invasive is very expensive.

EWM is native to Europe, Asia, and North Africa, but is now found on all the continents. It is widespread in North America, being found in 44 states and at least three Canadian provinces. It was first found in the states in 1942 in a Washington, D.C. pond and is thought to be brought here by the aquarium trade.

EWM typically grows in shallow waters, out to 15 feet, but has been found growing in 20 feet. It grows extremely rapidly right up to the surface in very dense mats and crowds out native plants. Two local sites where this is observable are, the bay in Lake Linden and Betterly’s Pond along Superior Road. It reproduces by seed or plant fragments cut by boat props or humans clearing their beach area of vegetation. Water birds can also spread it by carrying fragments to other water bodies, but boaters are the main source of new infestations. The EWM has 10-21 leaflets per stem, while native milfoil has nine or less. EWM also has reddish flower spikes.

Fish populations can also be affected to varying degrees, depending on the water body, as all are different. Many fish species need native vegetation for spawning, the survival of eggs/fry, and cover. An intensive fisheries study on a northern Wisconsin lake, where chemical treatments had been made from 2003 to 2012, found declines in numbers and recruitment. There, largemouth bass populations declined 91 percent, with none being younger than 7 years. Panfish numbers also declined by 75 percent. Northern pike and black crappie also showed no young fish. Many other studies, some of which were in the Lower Peninsula, also showed negative impacts on fish populations. The smaller the chemical treatment, the less impact on fish populations. Large treatments can cause major fish mortality during summer and winter when decomposing vegetation or algae blooms significantly reduces oxygen levels.

In extreme cases where the EWM tops out and literally covers the entire surface the physical act of fishing, boating or swimming is impossible. Even in less extreme cases, boat props can become entangled with EWM and damage the engine. Frequent stops to put in reverse and clean the prop are necessary. There have been deaths of swimmers reported due to very dense mats of EWM.

Property values decline where heavy EWM infestations are present. No one wants waterfront property where swimming, boating or fishing is difficult or impossible.

While yours truly is not fond of chemical treatments, many have to be done. Are there biological treatments available that work? The short answer is yes, but it depends on the water body. A native weevil can control EWM by laying their eggs in the stem, thus killing the plant. Two lakes in my former management area, Paradise Lake in Emmet County and Lake Saint Helen in Roscommon County were heavily stocked with milfoil weevils, with EWM being virtually eliminated. In other lakes it did not work.

Chemical treatments can be very expensive. Houghton Lake, our state’s largest inland lake, was given a whole lake treatment with flouridone. Cost was $1 million! Almost every inland lake in the LP has an EWM infestation to varying degrees. Many do chemical treatments, as it is a quick fix. Fix is the defining word, as once EWM infests a water body, periodic treatments will be necessary. Like getting hooked on drugs!

Who pays for all of this? Lakefront property owners, who set up special assessment districts to collect funds. The earlier EWM can be detected, the less expensive the initial treatment and subsequent “fixes.” In our area, the Torch Arm and Chassell Bay of Portage Lake are being treated to control EWM.

All boaters need to inspect their boats and trailers prior to going to another location. Prevention is cheaper than the cure. Do your part to stop the spread.

Go Fish!


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