THE ENEMY: Feathered Mosquito Fern (Azolla pinnata) is one of the new aquatic species that was recently added our noxious weed list. It has a small triangular leaf that has a marron looking margins which from a distance makes the entire colony appear like red velvet. This very small floating plant can spread rapidly, and has the ability to survive on moist soil in and around rivers, ditches, and ponds. The roots hanging below the leaves form feather like rootlets hence its name. Many times this plant spreads by fragmenting from the mature plant and starting its own colony. The upper surface of the leaves are totally water repellent and when submerged will float back to the surface quickly. The plant is great at fixing nitrogen in the water as is used in rice fields as a fertilizer in its native country.
THE STRATEGY: It forms dense surface mats, which degrade water quality by reducing oxygen levels, and can interfere with boating, fishing and recreational activities. The plant can spread rapidly and replace the native aquatic plants due to its great ability to float at all times. In a study by Duke University it was found to double in size every 5 to 7 days. Much more aggressive than anything that we currently have in our waters.
THE DEFENSE: Don’t move this plant from one site to another by transplanting it or by allowing it to hitch-hike onto your boat or other water enjoyment equipment. As it can survive over short periods of drought so it can also travel down the roadways. Once found and established one can try to remove the plants by harvesting it, but remember it spreads by fragmentation so getting all plants and plant parts is important. Some biocontrols have been tried with minimal success. This leaves us with using herbicides which is the most effective method on large patches. Products that are approved over water may include Navigate, Reward , and Sonar. Call your local weed professional for more information and positive identification and always clean your equipment 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.