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Eurasian watermilfoil (Myriophyllum spicatum L.)
ODA rating: B
USDA Symbol: MYSP2
Oregon Eurasian watermilfoil distribution
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Images courtesy of Center for Lakes & Reservoirs, Portland State University.

If images are downloaded and used from the ODA web site please be sure to credit the photographer.
Perennial, aquatic plant. Purplish red branching stems grow up to five feet long. Feather-like leaves in whorls of four at each node. Male flowers purplish and appear at the end of the flowering stem. Lower, whitish flowers female.
Eurasian watermilfoil has significant economic impacts to waterways, irrigation ditches, and drainage canals where it can inhibit flow and increase maintenance costs. It is also a pest of rivers, lakes and ponds were it reduces water quality, impeded recreation and boat access and have adverse impact to fish habitat. Elevated nutrient levels created by erosion, fertilizers or urban effluent create a rapid growth response that can render a waterway clogged within a short period of time. Expensive control projects frequently target this plant across North America.
Initial introduction is not certain, but it has been suggested that it was accidently introduced to Chesapeake Bay in the 1800s from Eurasia or northern Africa, probably with ship ballast
Distribution in Oregon
Common throughout western Oregon and the Columbia Basin. Infestations are known to exist in every state except South Dakota.

Biological controls
One biocontrol agent, the watermilfoil moth, has been approved for this plant.
Printable trifold Eurasian watermilfoil brochure (426kb)