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Eurasian watermilfoil (EWM) is an invasive species, native to Europe, Asia and North Africa, that has spread throughout the Midwest. EWM can create dense stands and dominate submergent communities, reducing important natural habitat for fish and other wildlife, and impeding recreational activities such as swimming, fishing, and boating.

EWM is typically at its peak growth stage during the latter part of the summer. Each year, the EWM population would be mapped during the late summer. These data can be seen in the 8-page EWM map book posted here.

Hybrid water milfoil (HWM) is a cross between the native northern water milfoil and the invasive EWM. In general, HWM has thicker stems, is a prolific flowerer, and grows much faster than pure-strain EWM. These conditions may likely contribute to this plant being less susceptible to being controlled by standard use rates of certain herbicides. HWM tends to interfere with recreation, navigation, and aesthetics more than pure-strain EWM populations. EWM and HWM have been confirmed from the Minocqua-Kawaguesaga system, with the MKLPA currently conducting research to learn more about the genetic composition of the invasive watermilfoil of the system.