Cason & Associates provides aquatic invasive species (AIS) management services to our clients. While newly established species are on the horizon, the two main AIS of concern are Eurasian watermilfoil and curly-leaf pondweed.


Eurasian watermilfoil (Myriophyllum spicatum) is an exotic submergent aquatic plant originally from Europe and Asia. It is an aggressive, rapidly growing plant that displaces native plants and clogs waterways. Eurasian watermilfoil poses serious threats to the ecological health and recreational value of lakes. Found in scattered areas throughout the U.S., the plant has recently invaded lakes in Wisconsin.

Threats to Recreation

Eurasian watermilfoil can grow to the surface in waters as deep as 20 feet. When mature, the plant forms a dense surface mat or canopy that may be thick enough for birds to walk on. Boating, swimming and fishing activities are often inhibited by this mass of vegetation.

Threats to Lake Ecology

Due to its aggressive early-season growth, Eurasian watermilfoil displaces nearly all native submergent plant species. Studies have shown that this reduced plant diversity results in a reduced diversity of invertebrates and other organisms that fish feed upon.

Threats to Fisheries

The extremely dense plant beds formed by Eurasian watermilfoil provide excellent cover for juvenile panfish – to the point where they are virtually inaccessible to predator fish. This typically results in overabundant, stunted populations of panfish. Correspondingly, growth rates of predator fish such as largemouth bass and northern pike are reduced.

Water Quality Impacts

Stagnant, oxygen-depleted conditions are often found in association with dense beds of Eurasian watermilfoil. The sudden nutrient release caused by the late-season die back of massive plant beds may also cause nuisance algae blooms.

Economic Impacts

Millions of dollars are spent annually to control Eurasian watermilfoil. Left unchecked however, the loss of real estate values and the losses to tourism and recreation-based industries would be far greater.


Curly-leaf Pondweed (Potamogeton crispus) is an exotic submergent aquatic plant native to streams in Europe and Asia. It was first documented in Wisconsin in 1905, and is now found throughout much of the U.S. Unique growth characteristics allow curly-leaf pondweed to have a competitive advantage over native plants. While not as aggressive as Eurasian watermilfoil, curly-leaf pondweed can achieve nuisance densities that impede recreation, threaten lake ecology and decrease water quality.


Unique Ecology

Curly-leaf pondweed begins growing in late fall and will grow under the ice. By spring, the plant will have a head start over native species. By early summer, curly-leaf pondweed often forms dense mats that reach the surface. At this stage, the plants have formed a vegetative reproductive structure called a turion. By late summer, usually August, adult plants die-off and decay, leaving behind the turions. When waters cool again in fall, these turions germinate – repeating the life-cycle.

Threats to Lake Ecology

One benefit of curly-leaf pondweed is that it provides winter cover for fish. However, its early-season growth gives it a competitive advantage that often causes it to displace important native plants. A late-summer die-off then, can lead to a sudden loss of habitat for fish and invertebrates.

Threats to Recreation

Dense beds of curly-leaf pondweed can clog boating lanes and inhibit traditional recreational uses, such as swimming, fishing, and sailing. Even waters that historically had limited plant growth due to high turbidity may develop nuisance levels of curly-leaf pondweed. The plant’s early-season growth often allows it to proliferate in lakes that may become too turbid for other species as the season progresses.

Water Quality Impacts

Dense plant beds may lead to stagnation, sediment accumulation and oxygen depletion. The greatest water quality impact of curly-leaf pondweed however, is caused by the plant’s massive die-off during the warmest time of year. The nutrient release from tons of rotting vegetation typically causes nuisance algae blooms and increased turbidity.


Prior to managing these invasive species, understanding their distribution and densities is important to designing an appropriate management plan. Cason & Associates conducts point-intercept and aquatic invasive species surveys to identify all invasive species within your lake. We will then provide you the maps and management recommendations that are specific to your lake and your budget. To learn more about our aquatic plant surveys, click here.

Contact us to learn more about managing the aquatic invasive species on your lake.