Overview

Eurasian watermilfoil (Myriophyllum Spicatum) is a plant native to Europe and Asia that was first documented in North America in the mid 1940s. Since its introduction, it has spread to more than 40 states in the US and to three Canadian provinces. Unfortunately, Eurasian watermilfoil has invaded many Northern Michigan lakes including Burt, Long, Paradise, and Walloon Lakes.

As Eurasian watermilfoil takes hold in a lake, it causes problems for the ecosystem and for recreation. It tolerates lower temperatures and starts growing earlier than other aquatic plants, quickly forming thick underwater stands of tangled stems and vast mats of vegetation at the water’s surface. These dense weed beds at the surface can impede navigation – and no one likes to swim in areas thick with aquatic plants. The lake ecosystem suffers because Eurasian watermilfoil displaces and reduces native aquatic plant diversity, which is needed for a healthy fishery. Infestations can also impair water quality due to dissolved oxygen depletion as thick stands die and decay.

A key factor in the plant’s success is its ability to reproduce through both stem fragmentation and underground runners. Eurasian watermilfoil spreads to other areas of a water body by fragmentation. A single stem fragment can take root and form a new colony. Locally, it grows by spreading shoots underground.

Boat traffic is responsible for the majority of introductions into new water bodies and for spreading the plant. Watermilfoils commonly become entangled in boat propellers, attach to keels and rudders of sailboats, and get caught up in boat trailers. Stems that become lodged in watercraft and trailers are transported to other water bodies, which is all that is needed to colonize new water bodies. Boats also contribute to unnatural seasonal fragmentation and the distribution of fragments throughout infested lakes.

Eurasian watermilfoil has difficulty becoming established in lakes with well established populations of native plants. In some lakes, the plant appears to coexist with native flora and has little impact on fish and other aquatic animals. Removing native vegetation, whether physically or with herbicides, creates the perfect opportunity for invading Eurasian watermilfoil.