STRATEGY: One of the worst Aquatic invaders is Eurasian Watermilfoil (Myriophyllum spicatum), a native of Europe, Asia, and northern Africa. This plant is a submersed perennial plant with finely dissected feather-like leaves. The leaves are arranged in whorls of four around the stem at each node and are about 1.2 inches long. The leaf generally has 12 or more leaflet pairs, the native plant Northern Watermilfoil will only have 8 pairs, and the stem will appear red.
ATTACK: This plant can single handedly destroy an entire lake ecosystem. The plant can root in water up to 30 feet deep. Once the plant reaches a certain size the dense mats will segregate themselves off of the bottom and float around the lake spreading seeds. This plant also spreads by fragmentation, that is, each time the plant is broken up by a propeller or boat it will start a new colony. Wildlife cannot swim through the dense mats, and children have even drowned due to getting caught up in them and not able to swim or stay afloat. When the dense mats start to break down by the bacteria it becomes harmful to fish. It spreads from lake to lake by getting caught on boats and trailers, and some suspect that waterfowl have contributed to the spread of the weed.
DEFENSE: Mechanical weed control is somewhat effective in controlling this weed, but is very expensive and requires scuba divers and gear. Many herbicides are available for use under careful and trained professionals which are approved for this use by the Environmental Protection Agency (EPA). The best control is to make sure your boats and gear is clean of debris when you pull out of the lakes. This weed has not been found on the eastern side of Idaho.
PLEASE NOTE – The proper use and application of herbicides can be an effective way to control and eradicate noxious and invasive plants. Before using herbicides, always carefully follow the label and safety instructions on the label. While we recommend the use of herbicides as one of the effective tools for integrated pest management, the Idaho Weed Awareness Campaign assumes no liability for herbicide applications.