Division of Boating and Waterways Begins Control Efforts in the Delta for Aquatic Invasive Plants



SACRAMENTO, Calif.— California State Parks’ Division of Boating and Waterways (DBW) announced today its plans for this year’s Aquatic Invasive Plant Control Program in the Sacramento-San Joaquin Delta and its southern tributaries. Starting tomorrow, March 1, DBW will begin herbicide treatments to control water hyacinth, South American spongeplant, Uruguay water primrose, Alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, hornwort (aka coontail), and fanwort.

These aquatic invasive plants have no known natural controls in the west coast’s largest estuary, the Delta. They negatively affect the Delta’s ecosystem as they displace native plants. Continued warm temperatures help the plants proliferate at high rates. Plants are also known to form dense mats of vegetation creating safety hazards for boaters, obstructing navigation channels, marinas, and irrigation systems. Due to their ability to rapidly spread to new areas, it is likely that the plants will never be eradicated from Delta waters. Therefore, DBW operates a “control” program as opposed to an “eradication” program. The division works with local, state, and federal entities to better understand the plants and implement new integrated control strategies to increase efficacy.

“Partnerships, technology, and monitoring efforts have helped the Division of Boating and Waterways better control the spread of aquatic invasive plants, such as water hyacinth and Egeria densa,” said DBW’s Deputy Director Ramona Fernandez. “Since eradicating them is impossible, the division and partners will continue to focus on reducing their negative impacts on people’s daily lives and businesses.”

All herbicides used in the AIPCP areregistered for aquatic usewiththe U.S.Environmental ProtectionAgency and the California Department of Pesticide Regulation.Treated areas for submersed aquatic vegetation (Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail/hornwort and fanwort)will bemonitoredto ensureherbicidelevels donotexceedallowablelimitsand follow EPA-registered label guidelines.Thepublic may viewthe public notices, treatment maps, and sign up to receive weekly updates on this year’s treatment season on DBW's website.

Below is a list of control actions for the 2023 treatment season:

Floating Aquatic Vegetation Control
Water hyacinth, South American spongeplant, Uruguay water primrose, and alligator weed.


  • Proposed Treatment Period: All Sites: March 1 – November 30
  • Type of Herbicides: Glyphosate, 2,4-D, Imazamox, or Diquat
  • Potential Treatment Areas: Initially in and/or around, but not limited to the following areas: San Joaquin River, Old River, Middle River, Fourteen Mile Slough, and Snodgrass Slough.

Mechanical Harvesting (If necessary)

  • Harvesting Dates: March – April and July – December
  • Mechanical Harvesting Sites: Select areas of the Delta with high infestations or coverage of water hyacinth.

Submerse Aquatic Vegetation Control
Brazilian Waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, ribbon weed, and fanwort.


  • Treatment Period: Starting March 1 through November 30, treatment period based upon DBW field survey data, water temperatures and fish surveys.
  • Type of Herbicide: Fluridone, Endothall, or Diquat.
  • Potential Treatment Areas: In and/or around the following areas (individual areas will be noticed prior to treatment application)
    • Anchorages, boat ramps and marinas: B & W Resort, Delta Marina Rio Vista, Grindstone Joes, Hidden Harbor Resort, Korth’s Pirates Lair, Oxbow Marina, Owl Harbor, River Point Landing, Rivers End, St. Francis Yacht Club, Tiki Lagoon, Tower Park Marina, Turner Cut Resort, Vieira’s Resort, Village West Marina, and Willow Berm.
    • Near Old River: Berkeley Ski Club, Bullfrog Ski Club, Cruiser Haven, Delta Coves, Diablo Ski Club, Discovery Bay, Golden Gate Ski Club, Hammer Island, Piper Slough, Sandmound Slough, Taylor Slough, Italian Slough, and Kings Island.
    • Sacramento Area: French Island, Hogback, Long Island Slough, Prospect Island, Sacramento Marina, Snug Harbor, and Washington Lake.
    • Stockton Area: Atherton Cove, Calaveras River, Bishop Cut, Honker Cut, Mosher Slough, Stockton Sailing Club, and Windmill Cove.
    • Antioch Area: Antioch City Marina, Lauritzen Yacht Harbor, and Sherman Lake Marina.

Mechanical Harvesting
This type of control method is not used for submersed aquatic vegetation. These plants spread by fragmentation. Cutting the plants back exacerbates the problem, as shreds of the plants float away and re-propagate.

Last year, DBW treated 1,636 acres of floating aquatic vegetation and 3,132.7 acres of submersed aquatic vegetation. No mechanical harvesting was conducted. A combination of herbicide, biological and mechanical control methods were used to help control invasive plants at high priority sites in the Delta.

Funding for DBW’s aquatic invasive plant control programs comes from the Harbors and Watercraft Revolving Fund, which receives revenues from boaters’ registration fees and gasoline taxes.

In 1982, California state legislation designated DBW as the lead state agency to cooperate  with other state, local and federal agencies in controlling water hyacinth in the Delta, its tributaries, and the Suisun Marsh. The Egeria Densa Control Program was authorized by law in 1997 and treatment began in 2001. In 2012, spongeplant was authorized for control upon completion of the biological assessment. In 2013, DBW was able to expand its jurisdiction to include other invasive aquatic plants, and since then other aquatic invasive plants such as Uruguay water primrose, Eurasian watermilfoil, Carolina fanwort, coontail, Alligator weed, and Ribbon weed have been added to the AIPCP.

To report sightings, subscribe for program updates or for more information regarding the control program, connect with us online at dbw.parks.ca.gov/AIS, via email at AIS@parks.ca.gov or by phone (888) 326-2822.

Photos from Division of Boating and Waterways.

Photos from Division of Boating and Waterways.

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