Eurasian watermilfoil (Myriophyllum spicatum) tolerates a variety of conditions; it can grow in fresh or brackish waters, a range of temperatures and soil pHs, and disturbed and polluted areas. It is typically found in ponds, lakes, and slow-moving rivers at depths of 3 to 33 ft. In Vermont, Eurasian watermilfoil is widespread throughout Lake Champlain and the state in general with populations documented in more than 80 waterbodies.
Eurasian watermilfoil is a submersed, rooted perennial plant. It has bright green, feather-like leaves arranged in groups of four around the stem. Each leaf is finely divided into 10 to 20 pairs of leaflets.
Each plant can have multiple stems, and stems branch near the water surface. Both stems and leaves often turn red in color at the water surface. Milfoil flowers in July and August and produces small, reddish flowers a few inches above the surface on spikes grown from the tips of the stems.
Eurasian watermilfoil’s tolerance of lower temperatures allows it to start growing earlier than other vegetation and form canopies that block light, which inhibits the growth of native plants and can lead to their displacement. It can also reduce the abundance and diversity of invertebrates.
In very shallow waterbodies, milfoil can grow from shore-to-shore and blanket the entire lake bottom and surface area of the waterbody, forming dense impenetrable stands with no open water. Only in these extreme and rare circumstances will recreational activities like swimming, boating, and fishing be impacted by Eurasian watermilfoil. Generally, this plant species has little negative impact on fish and wildlife with the greatest concern of this invasive species being on native aquatic plant diversity.
Besides the ecological impacts, infestations of milfoil have economic impacts through the reduction of property values and the high costs of various treatment options.
Control and Prevention
Despite a variety of treatment methods, Eurasian watermilfoil is nearly impossible to eradicate once it has invaded. Current control efforts include benthic barriers, mechanical harvesting, diver operated suction harvesting, biological control using watermilfoil weevils, and chemical treatment. Due to the high costs and continuous effort required, the best management option for milfoil is spread prevention. ]]>Eurasian watermilfoil was originally brought to North America through the aquarium trade and was introduced to lakes and ponds through aquarium dumping. The plant species is on the Vermont Noxious Weed Quarantine list, making it illegal to buy, plant, or transport milfoil in the state.
Milfoil easily spreads due to its ability to establish new plants from small fragments. Plant fragments are dispersed by water currents, animals, and people.
Because milfoil fragments can easily stick to boats and equipment, practicing the Clean, Drain, Dry spread prevention methods is very important. Drain all water from your boat, canoe, kayak, and other vessels and any equipment used in the water. Clean vessels and gear and remove all plant fragments and dispose of properly. Dry all damp areas of boats and vessels, such as livewells and bilges, with a towel and let air dry in the sun for at least five days before using in another waterbody. If this is not possible, rinse equipment with hot, high-pressure water.