For Immediate Release: 3/4/2022

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


SACRAMENTO, Calif. – The California State Parks’ Division of Boating and Waterways (DBW) today announced plans for this year’s control efforts for aquatic invasive plants in the Sacramento-San Joaquin Delta and its southern tributaries. Starting Thursday, March 17, DBW will begin herbicide treatments on water hyacinth, South American spongeplant, Uruguay water primrose, alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, and fanwort in the Delta. Treatment start dates may change depending on weather conditions and plant growth/movement.

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 and obstructing navigation channels, marinas and irrigation systems. Due to their ability to rapidly spread to new areas, it is likely the plants will never be eradicated from Delta waters. Therefore, DBW operates an Aquatic Invasive Plant Control Program (AIPCP) as opposed to an eradication program. The key to the success of the AIPCP is the division’s partnership with local, state, and federal entities to better understand the plants and implement new integrated control strategies to increase efficacy.

“DBW recognizes the negative impact of these aquatic invasive plants on people’s daily lives and businesses,” said DBW’s Acting Deputy Director Ramona Fernandez. “In an effort to minimize the impact, the division continues to leverage technology and resources through collaboration and cooperation with the public and local, state and federal partners who are helping us manage this challenge.”

A combination of herbicide, biological and mechanical control methods will be used to help control invasive plants at high priority sites in the Delta. All herbicides used in DBW’s AIPCP are registered for aquatic use with the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation. Treated areas for submersed aquatic vegetation (Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail and fanwort) will be monitored to ensure herbicide levels do not exceed allowable limits and follow EPA-registered label guidelines. The public may view the public notices and sign up to receive weekly updates on this year’s treatment season on DBW's website.

Below is a summary of the 2022 AIPCP treatment season:

Floating Aquatic Vegetation Control Program (Public Notice)
Water hyacinth, South American spongeplant, Uruguay water primrose, and alligator weed.

Herbicide Control

  • Proposed Treatment Period: All Sites: March 17, 2022 – Nov. 30, 2022
  • Type of Herbicides: Glyphosate, 2, 4-D, Diquat, Imazamox or Penoxsulam.
  • Potential Treatment Areas: Initially in and/oraround, but not limited to the following areas: San Joaquin River, Old River, Middle River, Fourteen Mile Slough, and Piper Slough. See priority maps for Northern and Southern treatment areas. 

Mechanical Harvesting (If necessary)

  • Harvesting Dates: March 2022 – April 2022 and July2022 – December 2022
  • Mechanical Harvesting Sites: Select areas of the Delta with high infestations or coverage of water hyacinth. See map for potential mechanical harvesting control areas.

Submersed Aquatic Vegetation Control Program (Public Notice)
Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail and fanwort.

Herbicide Control (Map)

  • Treatment Period: Starting March 17, 2022 through Nov. 30, 2022, treatment period based upon DBW field survey data, water temperatures and fish surveys.
  • Type of Herbicide: Fluridone or Diquat.
  • Potential Treatment Areas: Inand/or around the followingareas (individual areas will be noticed prior to treatment application):
    • Anchorages, boat ramps and marinas: B & W Resort, Berkeley Ski Club, Bullfrog Ski Club, Delta Marina Yacht Harbor, Hidden Harbor Resort, Hogback Boat Ramp, Korth’s Pirates Lair, Owl Harbor, Oxbow Marina, Rivers End, St. Francis Yacht Club, Perry’s Boat Harbor, Stockton Ski Club, Tiki Lagoon, Tower Park Marina, Turner Cut Resort, Vieira’s Resort, Village West Marina, and Willow Berm.
    • Near Old River: Cruiser Haven, Delta Coves, Diablo Ski Club, Discovery Bay, Golden Gate Ski Club, Hammer Island, Holland Riverside, Piper Slough, Quinn’s Slough, Sand Mound Slough, Taylor Slough, Italian Slough, and Kings Island.
    • Sacramento Area: Arrowhead Marina, French Island, Long Island Slough, Prospect Island, Sacramento Marina, Snug Harbor, The Meadows, and Washington Lake.
    • Stockton Area: Atherton Cove, Calaveras River, Calaveras Marina, Duraflame, Fourteenmile Slough, Mosher Slough, Stockton Sailing Club, and Windmill Cove.
    • Antioch Area: Antioch City Marina, Lauritzen Yacht Harbor, Martin’s Sherman Lake Marina, and New Bridge Marina.

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

Last year, DBW implemented a combination of herbicide, biological and mechanical control methods to help control aquatic invasive plants at high priority sites in the Delta. Approximately 2,500 acres of floating and 1,637 acres of submersed aquatic invasive plants were treated last year. No mechanical harvesting was conducted.

Funding for DBW’s AIPCP 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 aquatic invasive plants, and since then other aquatic invasive plants such as Uruguay water primrose, Eurasian watermilfoil, Carolina fanwort, coontail, and Alligator weed have been added to DBW’s AIPCP.

To report sightings, subscribe for program updates or for more information regarding the control program, connect with DBW online at, via email at or by phone (888) 326-2822.

Hyacinth and primrose blocking docks | Patch of invasive alligator weed | West Side Irrigation District Before Mechanical Harvesting | West Side Irrigation District After Mechanical Harvesting

Subscribe to California State Parks News via e-mail at

California State Parks provides for the health, inspiration and education of the people of California by helping to preserve the state’s extraordinary biological diversity, protecting its most valued natural and cultural resources, and creating opportunities for high quality outdoor recreation.