The Problem: Aquatic Invasive Plants, Toxic Herbicides, and Bad Permits

Invasive aquatic plants represent a serious problem for some Washington lakes. Unfortunately, many aquatic weed infestations are dealt with through the use of aquatic herbicides — chemicals that are applied directly to lakes and can seriously harm the ecosystem, endangered species, and threaten human health. 

Unfortunately for our lakes and salmon, the Washington State Department of Ecology unveiled a permit in spring 2006 that will give most lakes the ability have aquatic herbicides applied for five straight years, without any evaluation of non-toxic alternatives or monitoring of the impacts of the herbicides on the invasive plants, native plants, lake ecosystem, or human community.

This page has information about the many problems within this issue:

  • Invasive Aquatic Plants
  • Threats from Aquatic Herbicides
  • Problems with the State Permit

Common Invasive Aquatic Plants in Washington Lakes

One invasive aquatic plant that has become widespread in Washington’s water bodies is Eurasian watermilfoil (Myriophyllum spicatum), a fast-growing, feathery aquatic weed. Once sold as a popular aquarium plant, milfoil originated in Europe and Asia but has since become widespread across North America, arriving in lakes and streams as a stowaway on boat trailers. Milfoil can be identified by the many small divisions (generally around 12-20) on each leaflet and by the dense mats of vegetation that it can form on the surface, which may destroy salmon habitat and choke out native vegetation below.

Another problem plant for Washington is Brazilian elodea (Egeria densa), a bright green, robust plant with dense whorls of bushy leaves around the stem.  Leaves are 1-3 cm in length, and there are usually 4 or 8 leaves in each whorl. Like milfoil, Brazilian elodea can also form thick stands of vegetation in the water, covering hundreds of acres and choking out native plants in an area where it has become well established. Originally from South America, Brazilian elodea was also introduced to the United States as an aquarium plant.

Some other noxious aquatic weeds in Washington include : fanwort, fragrant water lily, hydrilla, parrotfeather, swollen bladderwort, water hyacinth, water primrose, and yellow floating heart. Also problematic (but not addressed here) are some wetland and emergent plants like garden loosestrife, purple loosestrife, and spartina. For more information on any of these plants, visit the Washington State Department of Ecology website at

Aquatic Pesticides 

Unfortunately, many aquatic weed infestations are dealt with through the use of aquatic herbicides, which are applied directly into the water to kill the invasive species. Although these chemicals are approved for use in the United States, many of them pose potential risks to human health and the environment. More significantly, direct application into the water means that these chemicals may drift away from the original treatment site, attacking a much larger area of the lake or pond and possibly affecting swimmers or wildlife in areas which may not have posted pesticide warnings. Additionally, it is not yet known just how long some of these chemicals may persist in the environment, or what the long-term effects of exposure may be. Here are some of the most common aquatic herbicides in use today, and some risks to consider:

2,4-D (brand names include Navigate®‚ Aqua-Kleen®, and others):
2,4-D is a relatively fast-acting, systemic herbicide (meaning that it kills the entire plant and root structure) which has been shown to be selective towards Eurasian watermilfoil. Although widely used in America and across the world, 2,4-D is considered to be “highly toxic” since it is a severe eye irritant know to cause irreversible damage. And because 2,4-D has high mobility in soil, it is able to travel through soil pathways and into groundwater, contaminating wells located near an aquifer or waterbody treated with 2,4-D.

In nature, 2,4-D has an adverse effect on a number of species. 2,4-D has been shown to reduce the rate of survival in ducks and waterfowl. 2,4-D is acutely toxic to fish, including salmon and especially juvenile salmon. Concentrations of less that 1 part per million of 2,4-D in water have been shown to be highly lethal to endangered Chinook salmon smolts and fry, and to juvenile pink salmon and chum salmon as well. It has also been shown to impair the ability of some salmon to capture food and develop normally. 2,4-D has exhibited detrimental effects on a number of other fish and wildlife species.

Diquat (brand names include Reward®, Aquakill®, Reglone®, and others):
Diquat is a fast-acting, non-selective herbicide that kills both invasive and native plants, destroying fish habitat and making it difficult for native species to re-establish themselves once an invasive plant has been removed. While an effective killer, Diquat is at best generally a temporary solution, since invasives will always return if there is no competition from native species.  

Glyphosate (brand names include Rodeo®‚ Roundup®‚ and others):
Recent studies have shown a strong correlation between exposure to Glyphosate and increased incidence of non-Hodgkin’s lymphoma (a type of cancer). In women, Glyphosate exposure has been linked to a higher risk of miscarriage during pregnancy, and to an increased risk of attention deficit disorder (ADD/ADHD) in children.

Fluridone (brand names include Sonar®‚ Avast®‚ and others):
Fluridone is a slow-acting systemic herbicide used to control underwater plants, a 7-12 week process during which time a constant level of concentration must be maintained in the waterbody. And like many other herbicides, Fluridone is non-selective, killing native plants along with target species and making it difficult for native species to re-establish themselves.

You can read more about potential hazards of these and other pesticides at:

Problems with the State Permit

In Washington state, the ability to use aquatic herbicides in lakes is regulated by the Department of Ecology under a National Pollutant Discharge Elimination System Permit (NPDES). In spring 2006, Ecology released the current NPDES permit. Unfortunately, the permit allows almost anyone to be approved to put herbicides into their lake. Here are some of the major problems with the permit:

  1. The permit allows each lake to treat annually for up to five years, the entire length of the NPDES permit, without needing any review by Ecology. This means that no one is required to check what impact the herbicides have had on the lake ecosystem or if aquatic weeds are even a continuing problem.
  2. There is no requirement for lakes to consider or use non-toxic alternatives before being allowed to use herbicides. Many effective non-toxic vegetation control methods are available in Washington. Read our non-toxic alternatives page for more information.
  3. Notification of neighbors is late and sorely inadequate. Anyone who is applying for coverage under the state permit (which allows them to use aquatic herbicides) is not required to notify their neighbors that the permit application has been submitted. Only if someone sees one of the small notices in a local paper would they know that they could comment on the permit application. No notices of the plans are posted locally until the permit coverage is granted and herbicide applications are already planned in 10 to 21 days.
  4. The permit is inappropriate for large lakes, like Lake Washington. The permit assumes that a broad section of a community would be engaged in the decision to use herbicides in the lake. However, for large lakes like Lake Washington, any property owner along the lake can apply for a permit to use herbicides in the lake without ever coordinating with or talking to their neighbors. There are no entities that coordinate vegetation management in Lake Washington, which led to upwards of 70 separate herbicide applications to the lake in 2004. See our page about Lake Washington  for more information on this problem and possible solutions.