| Eurasian watermilfoil |
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Eurasian watermilfoil (Myriophyllum spicatum L.)
ODA rating: B
Description
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.
Impacts
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.
Click on photo below to view larger image
| | Images courtesy of Western Society of Weed Science. | 
| If images are downloaded and used from the ODA web site please be sure to credit the photographer. Introduction
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.
Map legend
Yellow: limited distribution
Red: abundant
Grey: not known to be present
Biological controls
One biocontrol agent, the watermilfoil moth, has been approved for this plant.
Informational links
WeedMapper
Printable trifold Eurasian watermilfoil brochure (426kb)
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