For Immediate Release: 4/16/2020

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


The Division of Boating and Waterways (DBW) today announced its plans to control aquatic invasive species (AIS) in the Sacramento-San Joaquin Delta and its southern tributaries. Beginning on April 20, DBW will start herbicide treatments on floating aquatic vegetation (FAV) such as water hyacinth and alligatorweed, and submersed aquatic vegetation (SAV) such as Egeria densa and curlyleaf pondweed. Treatment start dates may change depending on weather conditions and plant growth/ movement.

These AIS 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. AIS such as water hyacinth are also known to form dense mats of vegetation creating safety hazards for boaters and obstructing navigation channels, marinas and irrigation systems. Due to the ability of AIS to rapidly spread to new areas, it is likely that 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.

“Controlling these aquatic invasive plants in the Delta continues to be a challenge,” said DBW Acting Deputy Director Ramona Fernandez. “The good news is that the Division of Boating and Waterways has seen a dramatic improvement in its control efforts due to the collaboration and cooperation with public and local, state and federal partners.”

Below is a list of proposed control actions for the 2020 treatment season:

Floating Aquatic Vegetation Control Program (Public Notice)

Water hyacinth, South American spongeplant, Uruguay water primrose and alligatorweed.

Herbicide Control

  • Proposed Treatment Period
    • Select Area 1 Sites and Areas 2-4: Apr. 20, 2020 – Nov. 30, 2020
    • All Area 1 Sites: June 1, 2020 – Nov. 30, 2020 (north of Hwy 12)
  • Type of Herbicides: Glyphosate, 2,4-D, Imazamox or Penoxsulam.
  • Potential Treatment Areas: Initially in and/ or around, but not limited to the following areas: San Joaquin River, Old River, Middle River, Fourteenmile Slough and Piper Slough. Map for treatment areas. 

Mechanical Harvesting (If deemed necessary)

  • Harvesting Dates: July 2020 – December 2020
  • Mechanical Harvesting Sites: Select areas of the Delta with high infestations or coverage of water hyacinth. Map for potential mechanical harvesting control areas.

Submersed Aquatic Vegetation Control Program (Public Notice)

Egeria densa, curlyleaf pondweed, Eurasian watermilfoil, coontail/hornwort and fanwort.

Herbicide Control (Map)

  • Treatment Period: Starting April 20, 2020 through November 30, 2020, treatment period based upon DBW field survey data, water temperatures and fish surveys.
  • Type of Herbicide: Fluridone 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, Hidden Harbor Resort, Korthen Pirates Lair, New Hope Landing/Wimpyte Marina, Owl Harbor, Oxbow Marina, Rivers End, Spindrift Marina, St. Francis Yacht Club, Tiki Lagoon, Turner Cut Resort, Vieira’s Resort, Village West Marina and Willow Berm.
    • Near Old River: Cruiser Haven, Delta Coves, Diablo Ski Club, Discovery Bay, Hammer Island, Piper Slough, Quin’s Island, Sandmound Slough, Taylor Slough, Italian Slough and Kings Island.
    • Sacramento Area: French Island, Long Island Slough, Prospect Island, Snug Harbor, The Meadows and Washington Lake.
    • Stockton Area: Atherton Cove, Calaveras River, Fourteenmile Slough, Mosher Slough and Windmill Cove.
    • Antioch Area: Winter Island and Emerson Slough

Mechanical Harvesting

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

A media call will be held tomorrow, April 17, to allow reporters to ask questions about the treatment plan.

      WHAT:      2020 Aquatic Invasive Plant Control Program

      WHEN:      Friday, April 17 at 10 a.m.

      WHO:        Division of Boating and Waterways staff and partners.

      CALL:       (888) 989-3381   I   Code: 9591296

DBW works with local, state and federal entities to better understand the plants and implement new integrated control strategies to increase efficacy.

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 will be monitored to ensure herbicide levels do not exceed allowable limits and follow EPA-registered label guidelines. Notices were made available to the public on April 3, 2020. They may be viewed online on DBW's website.

Last year, DBW treated 3,885 acres of FAV and 2,406 acres of SAV. Mechanical harvesting efforts totaled approximately 6.49 acres. A combination of herbicide, biological and mechanical control methods were used to help control the AIS in the Delta. Infestation of FAV over the last three years has lessened due to treatment. Currently, the Delta waterways are still clear and open from FAV and SAV infestations.

The plants now are just starting to begin the early stages of growth as the weather continues to warm, which is the optimal time to begin treatment. For this year’s treatment season, it is imperative that treatment crews focus on the alligatorweed plant to control and attempt to eradicate this newest invader of the Delta. Alligatorweed breaks apart and spreads easily; each node, which is roughly the size of a Cheerio, can start a new plant.

During these trying times of COVID-19, DBW’s AIS control efforts in the Delta have been deemed essential. All staff have been trained on how to carry out their duties while following health and safety protocols. As the State of California continues to issue guidance on preparing and protecting all Californians from the pandemic disease, the California Department of Parks and Recreation is monitoring the situation closely and is following guidance provided by the Governor’s Office via the California Department of Public Health, the Centers for Disease Control and Prevention, and the Governor’s Office of Emergency Services.

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 the former Department of Boating and Waterways 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, the Division of Boating and Waterways was able to expand its jurisdiction to include other AIS. Uruguay water primrose, Eurasian watermilfoil, Carolina fanwort, coontail/hornwort and alligatorweed have been added to the AIPCP.

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

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