Skip to Main Content
Contact Us Search
OHP Title

Submersed Aquatic Vegetation


Egeria densa (Brazilian Elodea) is a shallow-water submerged aquatic plant from Brazil, popularly used as an aquarium accessory that was introduced into the Sacramento-San Joaquin Delta about 40 years ago (possibly from use in home aquariums). Egeria densa and other submerged vegetation now infest many thousands of surface acres of the Sacramento-San Joaquin Delta. The plant can spread very quickly depending on environmental conditions, often by fragmentation. The Division of Boating and Waterways (DBW) is the only entity authorized to treat Egeria densa in California with herbicides.

Egeria Densa

Egeria Densa

  • Submerged aquatic perennial
  • 3-6 leaves, whorled
  • Middel and upper leaves 15-40 mm long, 2-5 mm wide
  • Small white flowers extend up to 3 cm above water surface.
  • Native to South America

Growth Period: spring-late fall

Control Methods Currently Used by DBW:
  • Chemical Control
Habitat: slow-flowing or still water in sloughs, canals, rivers, ponds, lakes, and reservoirs; often in nutrient-rich substrates.


Curlyleaf Pondweed


  • Leaves are floating and/ or submersed
  • Wavym stiff and crinkled leaves 50-76 mm long
  • Develop turions (specialized stem buds that survive unfavorable conditions)
  • Turions resemble brown pinecones 7-25 mm long
  • Native to Eurasia

Growth Period: early spring-late summer 

Control Methods Used by DBW
  • Chemical Control

Habitat: ponds, lakes, streams, rivers, reservoirs, irrigation ditches, and marshy areas.


Members of the public may contact DBW with questions or concerns relating to Egeria densa and treatment of this aquatic invasive species at (888) 326-2822 or e-mail the division at Include in your message the address or nearest landmark of the sighting. If possible, take photographs of the plant.

Program Restrictions

For treatment, three permits are required to be obtained. These permits place restrictions on where and when DBW can treat the aquatic invasive weed (this varies throughout the Sacramento-San Joaquin Delta), establishes the chemical concentrations allowable in treated areas and requires extensive water quality monitoring.

Two permits are required by the federal Endangered Species Act from the United States Fish and Wildlife Service and the National Marine Fisheries Service (part of the National Oceanic and Atmospheric Administration).

A third permit, a National Pollutant Discharge Elimination System permit is required by the Central Valley Regional Water Quality Control Board.


Current and Potential Treatment Areas

The California Department of Parks and Recreation Division of Boating and Waterways
will be conducting herbicide treatments in parts of the Sacramento-San
Joaquin Delta region to control Brazilian waterweed (Egeria densa) and curlyleaf
pondweed (Potamogeton crispus).

The following information is subject to change based on governmental requirements,
weather conditions, plant growth, waterway traffic, special status species
surveys and other conditions.

Proposed Herbicide Treatment Period
March 1, 2017 – July 2017
Treatment period is based upon DBW field survey data, water temperatures, fishery
surveys and other conditions.

Potential Treatment Areas*
In and/or around the following areas:

Anchorages, boat ramps and marinas: Willow Berm, Korth’s Pirates Lair, Perry’s
Boat Harbor, Rivers End, Big Break Marina, Delta Marina Rio Vista, B & W Resort,
Vieira Resort East, Sacramento Marina, and Snug Harbor.

Near Old River: Latham Slough, Old River, Discovery Bay, Piper Slough, Sandmound
Slough, and Taylor Slough.

Stockton Area: Atherton Cove, Duraflame, Buckley Cove, Fourteenmile Slough,
Mosher Slough, Pixley Slough, Disappointment Slough, Bishop Cut, White
Slough, and Honker Cut.

Sacramento Area: The Meadows, Cache Slough, Barker Slough, and Lindsey
See map for treatment areas.
*Individual areas will be noticed prior to treatment application. If all listed sites can
be treated, acreage will total 3,242 acres.

Herbicides Being Applied
Fluridone (Herbicide is registered for aquatic use with US Environmental Protection
Agency and the California Department of Pesticide Regulation)

The public should not gather on or near boat docks during treatment applications.
Boaters, swimmers, fisherman and other recreationists in an area being immediately
treated are urged to heed directives, as they are aimed at protecting public safety,
by herbicide technicians.

Treated areas will be monitored weekly to ensure herbicide levels do not exceed
allowable limits, or have any significant adverse impacts on the environment, agriculture,
or public health in or near the above mentioned treatment areas.

Contact Information
To report sightings or for more information regarding the control program, please visit DBW's website at, call (888) 326-2822 or email us at

DBW Authority to Treat and FAQ about Treatment

Egeria densa is a shallow-water submerged aquatic plant from Brazil. It is a bushy plant with dense whorls of bright green leaves (except when growing with insufficient light, in which case the leaves are widely spaced). Egeria densa usually has four leaves per whorl (arranged around the stem) and each leaf is at least 2 cm long.
There is no known eradication method in the world for Egeria densa. Therefore, DBW operates a "control" program as opposed to an "eradication" program.
This aquatic invasive plant can negatively impact a waterways ecosystem. It displaces native plants, blocks light needed for photosynthesis, reduces the amount of dissolved oxygen in the water and deposits silt and organic matter several times the normal rate.
The plant has a significant impact on recreation and commercial activity. Dense mats of vegetation create safety hazards for boaters, obstructing navigation channels, marinas and irrigation systems.
The plant can spread at a rate of approximately 100 acres a year depending on environmental conditions. Egeria densa spreads by fragmentation. For example, cutting the weeds back only exacerbates the problem, as shreds of the plant float away and re-propagate.
Egeria densa is a popular aquarium accessory. It was introduced into the Sacramento-San Joaquin Delta roughly 40 years ago, possibly from use in home aquariums.
Thousands of acres are infested by Egeria densa in the Delta.
A good sign that the herbicide is working effectively is that the growing tips of the plant will turn a pale pink or white.
Harbors and Navigation Code, Article 2, Section 64 provides that DBW is designated as the lead agency of the state for the purpose of cooperating with agencies of the United States and other public agencies in controlling water hyacinth and Egeria densa in the Sacramento-San Joaquin delta, its tributaries, and the Suisun marsh. State funding for controlling water hyacinth and Egeria densa is appropriated in California's annual Budget Act.
The Egeria densa program was authorized by law in 1997. Treatment for Egeria densa began in 2001.
Funding for the Egeria densa treatment comes from the Harbors and Watercraft Revolving Fund, which receives revenues from boaters' registration fees and gas taxes.