INVASIVE SPECIES – EUROPEAN FROG BIT
It’s 2015, and we’re still removing European frog-bit by hand.
This aquatic invasive species was brought over from Asia and Europe as an ornamental pond plant in 1932. In 1939, this species planned its escape from the Arboretum of the Central Experimental Farm in Ottawa where it was commercially grown. It crept down through Ottawa River, made its way to Ontario’s south shore and can now be found in Lake St Clair and the Detroit River with more recent sightings in the Alpena area.
The heart-shaped leaves and leathery feel of European frog-bit (Hydrocharis morsus-ranae) is what distinguishes it from other native species. The leaves are no more than one to two inches wide, and hold a deep purple color on the underside and a bright green on top. One single white flower with three petals is produced by the plant. Its root system hangs suspended in the water. A single plant can create 100-150 buds during one season, which break off the plant and lie dormant on the mucky bottom until spring when they will float back to the surface and regenerate.
If you find yourself in standing water with low wave energy, you may find yourself standing next to European frog-bit. The plant prefers quiet water such as drainage ditches, marshes, or swamps. It has difficulty inhabiting areas with high wave energies because it is a floating plant and not firmly rooted in soil or the water’s bottom.
Once established, however, this aquatic invasive species can quickly wreak havoc on an ecosystem. European frog-bit forms thick, dense mats of vegetation that make it difficult for sunlight to penetrate the water and provide energy for other plant species. Fish find it difficult to swim through these patches, as do waterfowl and recreational boaters. As the masses of these frog-bit colonies die and decompose, they can quickly change the oxygen levels of the surrounding waters which may result in the death of fish and native vegetation. 
Control of the species is currently best available through mechanical controls, such as the removal by hand. However, the removal by hand does not guarantee that frog bit will not return, it simply removes the present plants from the ecosystem. There are herbicides that can control the spread of the species, but they may not be effective. The absolute best control of this species is prevention. It is suspected that recreational boaters are the prime source of the spread. It is vitally important that you always check your boat and boating equipment for any “hitchhikers” you may have picked up. For a species such as frog-bit, it is easy to spot the lilies and roots hanging off propellers and other rough edges. Make sure to drain all the water out of live wells, motors, and bilges, and thoroughly wash your boat and equipment before transporting it to a new lake. Currently high populations of frog bit reside in Monroe, St. Clair, Macomb, Bay and Wayne Counties. Through the help of anglers and the greater conservation community, we can control the spread of European frog bit in the Great Lakes.
For a free aquatic invasive species field guide, visit http://mnfi.anr.msu.edu/invasive-species/AquaticsFieldGuide.pdf
Report sightings of European frog bit to Kile Kucher – DNR Wildlife Division, KucherK@michigan.gov or 517-641-4903, ext. 243.
