Delta Ponds Ludwigia Control
Ludwigia hexapetala or Uruguayan primrose willow is an invasive aquatic plant originally from South America. It is possible that this plant was introduced to this area when someone dumped the contents of a fresh-water aquarium into the ponds which contained a young live aquarium plant.
The City of Eugene has been controlling Ludwigia at Delta Ponds since 2009. Early efforts were experimental and consisted primarily of hand pulling aquatic plants. In 2013, the City applied for grant funding from the Oregon State Weed Board (OSWB) to assist with control efforts. Since then, the City of Eugene, in partnership with the OSWB, has been aggressively controlling Ludwigia using an integrated approach that utilizes a combination of hand pulling and careful spot spraying of shoreline plants with Salmon Safe-approved herbicide. The City has been able to reduce this invasive aquatic weed by over 90%, however control is an on-going effort to prevent Ludwigia from taking over again.
Join Eugene Outdoors for Pull and Paddle events where volunteers learn about, search for and pull aquatic invasive plants while paddling a canoe. No experience is necessary and volunteers are welcome to bring their own boat, but registration is required. Tools, gloves, instruction, snacks, canoes, life vests and paddles provided. See the calendar of events for upcoming volunteer opportunities.
- It doubles its biomass in 15 to 20 days, forming dense mats both above and below the waterline which then chokes out entire waterways.
- Western pond turtles, fish, ducks, and other wildlife cannot swim through infested areas, limiting available habitat.
- In addition to spreading by seed, it reproduces from plant fragments that break off and migrate downstream, infesting new waterways.
- Dense mats of Ludwigia block sunlight from the water’s depths, killing off native aquatic plant species essential to sustain local wildlife.
- Large mats die back in early winter, depleting the oxygen levels in the water.
- Without adequate oxygen, juvenile Chinook salmon that use the Delta Ponds as over-wintering habitat will be impacted and may even die.
This infestation is the most upstream population on the Willamette River and has the potential to spread downstream and invade the Willamette watershed. The invasive nature of this plant has the potential to undo all of the recent environmental and economic efforts to improve habitat at Delta Ponds for juvenile Chinook salmon and Western pond turtles.