What Eats Eurasian Milfoil?

Description

• The Eurasian water filmoil is native to Europe, but has quickly spread through freshwater lakes of the United States since its arrival in 1940. It is a resilient species that thrives in a range of conditions but prefers bright light, fine sediment, and a low organic content in the sediment. Its feather-like leaves are arranged around it stem, with about 12 or more leaflet pairs on each leaf. At times, its growing tips are red in color. Pinkish flowers emerge above the water surface during pollination.

Invasiveness

• This species is highly-destructive to freshwater body habitats of the United States and is considered one of the most problematic water species in many regions. With the species present, dense mats of vegetation appear on water surfaces and interfere with ecological and human activities. These canopies shade out other aquatic plants, prevent wind-based oxygenation of the water and increase sedimentation. Due to the ease of its reproduction, the Eurasian milfoil quickly takes over a water body, infesting a lake within two years of its introduction. The plant raises pH, increases phosphorus and nitrogen and increases water temperature, diminishing habitat quality for fish, birds and other creatures. For these reasons, scientists are very interested in species that could consume the plant and control its spread.

Insects

• Scientists have studied the creatures that consume the milfoil extensively, with hopes of establishing biological control by releasing those species. The most promising of the insects is the milfoil weevil. It is a plant-eating beetle that feeds only on species of milfoil, including the Eurasian milfoil, eating its stems and leaves. It will lay its eggs on the plant and its hatchlings will eat the plant as well. Other insects that consume the plant include pyralid moths, stem-boring weevils and the midge (a type of fly).

Fish and Birds

• The triploid grass carp is a herbivorous fish species that lives in large freshwater lakes alongside the milfoil. It will consume the Eurasian milfoil when no other aquatic plants are available, but it does not consider the plant highly palatable. As a method of biological control, the carp is only useful if the Eurasian watermilfoil is the only plant in the lake. If it is released in a lake with more preferable species, it will consume all the other plants before the milfoil.

  Some species of waterfowl consume Eurasian milfoil. In fact, one study published in the journal "Estuaries" in 1995 suggests that the introduction of the plant helped support populations of certain birds, including dabbling ducks, American coot and ring-necked ducks.