What is Ludwigia? 
Articles written by Metro staff and do not necessarily represent the opinions of Metro or the Metro Council.
Invasive ludwigia is an aquatic plant native to South America. Officials in Oregon started noticing a dramatic growth in ludwigia about five to seven years ago, likely after people dumped out aquariums with ludwigia in local waterways.

Ludwigia has several species and subspecies of ludwigia. Most of the ludwigia found along Willamette River backwaters is Ludwigia hexapetala, sometimes called water primrose or primrose willow. The kind found at Smith and Bybee Wetlands is Ludwigia peploides montevidensis. Ludwigia peploides is sometimes called floating primrose willow.

One kind of ludwigia is native to Oregon – Ludwigia palustris – but the plants are much smaller than the invasive varieties, and they do not compete with other native plants. The native ludwigia is sometimes called eastern false loosestrife or marsh seedbox.



This is invasive ludwigia, an aquatic plant native to South America that is threatening to choke backwaters, oxbow lakes and warmer river channels in Oregon. Ludwigia could destroy these special habitats and harm water quality, damaging native plants, amphibians, fish, birds and other wildlife. But it’s not too late to avoid the worst, and a network of groups is battling ludwigia.

Ludwigia is the worst invasive aquatic plant in the state, said Glenn Miller, an invasive plants specialist at the Oregon Department of Agriculture.  “As I say to people in lectures, this one is the game changer,” he said. “It is so impactful that you’ll see open bodies of water that just convert to anaerobic mudholes in probably 20 years and really exclude most other life. No other aquatic plant we have had in the state does that.”

State officials first noticed a significant increase in invasive ludwigia about five to seven years ago when it started infesting Willamette River backwaters, such as Delta Ponds in Eugene. Since then, there have been infestations at
Willamette Mission State Park near Salem, near Willamette Falls, Smith and Bybee Wetlands and other parts of the Willamette River system. Infestations have also been spotted in the Columbia Slough in Portland, Rogue River system in southern Oregon and in Central Oregon.

“The entirety of western Oregon and up through the Columbia River system and some parts of central and northeastern Oregon could be really susceptible to it,” Miller said.  Experts suspect ludwigia arrived in Oregon through the aquarium and aquatic garden trades. The plant is popular in aquariums, which often get dumped into local waterways when people no longer want them.”

Help tackle ludwigia: Interested in joining the fight against invasive ludwigia?

*Please clean, drain, and dry boats and gear after all outings on water
*If you spot invasive ludwigia, report it to the
Oregon Invasive Species Hotline
*Join the Willamette Aquatic Invasives Network and contribute to a community map of ludwigia

Native plants form the basis of healthy habitats that provide food and shelter for native animals. For instance, Smith and Bybee Wetlands is an important stopover for migratory birds to rest and refuel as they fly to and from the Arctic. But when invasive ludwigia covers an area, migrating shorebirds can’t stick their beaks in mudflats to eat bugs, and wintering ducks and waterfowl find less rice cutgrass and other native seeds and plants.

Ludwigia can also lead to poor water quality, said Elaine Stewart, a senior natural resources scientist at Metro. The dense mat of ludwigia on the water surface and decomposition as it dies deplete oxygen from the water. Low oxygen is bad because native fish and invertebrates that live in the wetlands need oxygen. It could also make water quality bad for salmon.

“Ludwigia can throw an entire ecosystem out of balance,” Stewart said. “Complexity is good in an ecosystem, and ludwigia simplifies it.”

A network of people is trying to prevent that from happening in the Willamette River system. Formed in 2014, the
Willamette Aquatic Invasives Network meets quarterly, and members represent more than 60 government agencies, land trusts, nonprofits, universities, businesses and community members.

The network is forming a steering committee to develop a comprehensive aquatic invasive species action plan, said Marci Krass, the network coordinator and restoration program manager at the nonprofit
Willamette Riverkeeper.

“There’s a lot of enthusiasm in helping to save these backwater habitats,” said Matt Mellenthin, a network member and a habitat restoration coordinator at
Integrated Resource Management, a company based in Philomath. “Just about everybody in the environmental field clearly sees how important the habitats being taken over by ludwigia are. Whether it’s for salmon rearing or water quality, there are just a lot of partners working on this stuff together.”

“The first year we worked at Delta Ponds (in Eugene), it was the first large-scale ludwigia treatment in Oregon,” Mellenthin said. “In a five-year span, we’ve gone from one project to 13 large projects throughout the Willamette Valley, from Eugene to Smith and Bybee.”

Invasive ludwigia can also significantly reduce recreational opportunities. Infested areas often cannot be accessed by motorized or nonmotorized boats.

  • Small fragments of ludwigia can easily spread and grow, causing new infestations downriver.

  • Ludwigia peploides montevidensis leaves can appear more pointed when growing on land.

  • Ludwigia hexapetala leaves can appear more rounded when growing on water.


Increased DEQ pesticide authority worries farm groups.
Mateusz Perkowski,Capital Press

Agriculture and forestry groups in Oregon worry the state’s Department of Environmental Quality is planning to significantly expand its authority over pesticides.Under the policy being considered by DEQ, the agency would regulate pesticide spraying over state surface waters “whether wet or dry at the time,” according to an early draft. It’s unclear how broadly dry waterways would be defined, but the concern is that areas where water pools in winter — such as wet fields in the Willamette Valley — would be subject to regulation during summer, critics argue.

“DEQ would be setting itself up to be the most aggressive regulator of farm and forestry practices in the U.S.,” said Mary Anne Cooper, public policy counsel for the Oregon Farm Bureau.

Regulation of pesticides over waterways by DEQ initially became an issue in 2009, when the 6th U.S. Circuit Court of Appeals overturned a federal policy exempting pesticides from regulation under the Clean Water Act.
The U.S. Environmental Protection Agency delegates its Clean Water Act authority to certain states, including Oregon, which developed a “general permit” for pesticide discharges in 2011.

This original policy wasn’t a problem for farmers and foresters, though, because it largely just required them to follow the EPA pesticide label and general “integrated pest management” standards, said Scott Dahlman, policy director for the Oregonians for Food and Shelter agribusiness group.

“It formalized what these guys are already doing,” Dahlman said,
“Most people were covered but didn’t know it,” added Cooper.

That original general permit expired in 2016, which prompted DEQ to begin devising an updated version.
The Oregon Farm Bureau and Oregonians for Food and Shelter are concerned by proposed drafts they’ve discussed with DEQ, which indicate dry waterways would be defined broadly, requiring many more farmers to register with the agency and submit pesticide management plans.

“We’re seeing no justification as to why this is necessary,” said Dahlman.

Even if the DEQ wouldn’t enforce the general permit as applying to every dry puddle, the program would fall under the federal Clean Water Act, which allows for private litigation over alleged violations, Cooper said.
“There would be citizen suit enforcement,” she said.

If the DEQ seriously extended its authority over pesticide spraying, that would also effectively usurp the Oregon Department of Agriculture’s jurisdiction under the agricultural water quality program, Cooper said.
Growers have been encouraged to advise ODA on water quality plans and voluntarily improve water conditions on their properties, which would be undermined by DEQ’s planned policy, she said. “That’s a big betrayal of trust for a lot of farmers.”

Ron Doughten, water quality permitting manager for DEQ, said the agency is in the process of addressing comments about the general permit.

The agency is still analyzing which pesticide applications would be considered to come from “point sources” — opening them to Clean Water Act regulation — and which waters would be covered by the permit, whether wet or dry, Doughten said.

“How and where that applies is still a part of the discussion,” he said. “We’re far from anything being settled.”
The agency plans to release its most recent draft of the permit for public comment in late winter or early spring, then finalize the policy within several weeks, Doughten said.

Beyond Toxics, an environmental group, believes Oregon’s oversight of pesticide spraying should be strengthened, said Lisa Arkin, its executive director.  “Pesticides are persistent in the environment and should be regulated as a point source pollution problem,” she said.

In meetings with the DEQ, however, the organization did not discuss regulating dry waterways as broadly as critics worry about, Arkin said. “We were talking about small streams and irrigation ditches. We were not talking about depressions in a field,” she said.

Even so, farmers should be extremely cautious about potentially contaminating well water with pesticides, some of which can persist in water for up to five years, Arkin said.

“There is so much evidence of contamination of well water in agricultural areas,” she said.
Farmers typically buy pesticides from large suppliers, or are serviced by specialized applicators, so it wouldn’t be problematic to inform them of new general permit requirements, Arkin said. “There are many ways people could be alerted to that.”
Guidelines for Stream and Ditch Maintenance
ODA Ag Water Quality Program

Molalla Oregon Pesticide Waste Collection Event

This is a one-time free pesticide waste collection event for farmers, growers, and other commercial and institutional pesticide users located in the Northern Willamette Valley. The collection is scheduled for

Friday, June 1, 2018 at Bolander Field, Molalla
Copyright © 2018 Marion Soil and Water Conservation District, All rights reserved.

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