The Strategy - Parrotfeather milfoil (Myriophyllum aquaticum) is an introduced aquatic plant that is listed as a noxious weed. It was brought here as an ornamental for small ponds, aquariums, or worse Geothermal warm pools, then formed large colonies that covered all open water of ponds and small lakes. Like its relative, Eurasian water milfoil, this plant can regenerate by fragmentation. Thus, broken off plants can float for long distances and start new colonies. This plant has creeping rhizomes that originally produce fibrous roots at the nodes. It has bright green leaves with 13 leaflet pairs or more in 5-6 whorls around the stem. It has been found in Western Idaho.
The Attack - The mats of weeds are formed on the surface and the subsurface, which chokes out all living material such as native plants and fish. Not only are the large floating mats harmful to fish and native plants, they are almost impossible to boat through as the weeds bind up the propellers and plug the jets on boats. The plant is also easily spread by getting caught on trailers and in the bilges of boats, thus making clean up once leaving the water much more difficult.
The Defense - Clean up your boat, trailer, float tube, waders, nets, fishing devises and any other place you think that the plant can hang onto. This weed is spread from water body to water body by users of waters, even waterfowl have been thought to move this weed around. Once a lake is contaminated mechanical harvesting is possible, but very expensive and time consuming. Aquatically approved herbicides are available such as Navigate (2,4-D) and Renovate (Garlon) are very effective if applied right. Remember to always clean you trailer and boat when leaving a water body.
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.
For more information, click on the link below to download the Idaho's Noxious Weeds Control Guidelines publication produced by the University of Idaho Extension.
U of I Idaho's Noxious Weeds Control Guidelines (183 KB PDF download)