Invasive Species

Invasive Species lack the predators and diseases that kept their numbers in check in their native ranges, so they are often able to out-compete and out-reproduce native flora and fauna. Over time, an invasive species can disrupt an ecosystem, causing severe changes to the biodiversity and ecological processes that had existed for centuries.

Programs like Clean Boats, Clean Waters, which seeks to prevent new species introductions, are the most effective tools to combat invasive species.

Here are some brochures to help in identifying invasive plants:
  • WI DNR Common Invasive Wetland Plants Guide
  • "Plants out of Place" from the Great Lakes Indian Fish & Wildlife Commission (GLIFWC)

    • Known Invasive Species in Bear Lake:


    Purple Loosestrife (Lythrum salicaria)

    Purple Loosestrife flower spikes.

    Purple Loosestrife is very hardy and reproduces with remarkable speed. A single plant can produce millions of seeds each season, and seeds remain viable in the lakebed for 5 years. It can quickly crowd out native plants, forming dense monocultures and reducing habitat and food sources for native wildlife. Purple Loosestrife has been present in Bear Lake since the 1990s and stopping its spread is a top priority for the Lake Association.

    Purple Loosestrife grows in wetlands and the shallow areas on the edge of waterbodies. It can range from 3 to 7 feet tall, with multiple woody stems with 4 to 6 distinct sides. From early July to September, a "spike" appears at the top of the plant from which many 5- or 6-petaled purple to magenta colored flowers grow. Note that there are several native plants with blooms similar in color to Purple Loosestrife.     Bear Lake Association volunteers have been actively working to identify and manually remove Purple Loosestrife from the lake for almost 20 years. Additionally, volunteers have been raising and releasing Galerucella beetles into existing stands of Purple Loosestrife. These beetles were the plant's natural predators in Europe, and they only eat Purple Loosestrife. The beetles can inflict severe leaf damage, leaving the plant without enough energy to flower and reproduce.

    If you are interested in getting involved with raising and releasing beetles, or you think you've found a new stand of Purple Loosestrife on Bear Lake, please call Bob and Dorothy Moe at 715-234-7095 or get in touch with us here.

    Curly-Leaf Pondweed (Potamogeton crispus)


    Curly-Leaf Pondweed has been documented in Bear Lake since 1992, and is mostly found in the far northwest basin and in and around the outlet to Bear Creek at the southeast end of the lake. It thrives in shallow areas up to 15 feet deep, and is usually the first aquatic plant to be visible in the spring.

    Its life-cycle is unique in that it starts to grow in late fall and can stay green underneath ice. By getting a head start on the growing season, it is able to crowd out slower-growing native plants and form dense mats in spring and early summer that interfere with recreation. The bulk of the plant dies off as the weather warms in June and July. In areas where Curly-Leaf Pondweed is a dominant plant, this early-summer die-off can cause algal blooms.


    Banded Mystery Snail (Viviparus georgianus) & Chinese Mystery Snail (Cipangopaludina chinensis)

    L to R: Banded, Brown (native), & Chinese Mystery Snails

    Invasive Mystery Snails are commonly found in shallow areas of Bear Lake, often clinging to rocks. There is some uncertainty as to their ecological impact, but it is likely that both varieties of invasive Mystery Snail compete with other native snails and filter-feeders. They have also been linked to a parasite that is lethal to native waterfowl.


    Common Reed (Phragmites australis)

    Common Reed was observed in two locations on Bear Lake during plant surveys in 2013. It is not considered problematic at this point, but the Lake Association will continue to monitor Common Reed in the coming years. Similar to other invasive aquatic plants, Common Reed is capable of forming dense monocultures that crowd out native species and alter ecosystems.


    Japanese Knotweed (Fallopia japonica)

    Japanese Knotweed (Fallopia japonica) has been identified in several riparian areas along Bear Lake and is being chemically under the guidance and assistance from the Barron County Soil and Water Conservation Department.


    Yellow Flag Iris (Iris pseudacorus)

    Yellow Flag Iris (Iris pseudacorus) has been identified in one riparian area along Bear Lake and has been manually removed under the guidance and assistance from the Barron County Soil and Water Conservation Department.



    Invasives present in Northwest WI, NOT known to be in Bear Lake:


    For more information, see the 2014 Bear Lake Aquatic Plant Management Plan and the UW-Extension Citizen Lake Monitoring website.