For Immediate Release: 2/15/2017

DBW Begins Herbicide Treatment in the Delta for Water Hyacinth and Egeria densa


Contact: Gloria Sandoval  I  (916) 651-7661


Sacramento, Calif. -- California Department of Parks and Recreation Division of Boating and Waterways (DBW) will begin herbicide treatment of South American spongeplant (Limnobium laevigatum), Uruguay water primrose (Ludwigia hexapetala), water hyacinth (Eichhornia crassipes), curlyleaf pondweed and Brazilian waterweed (Egeria densa) this Wednesday, March 1, in various areas of the Sacramento-San Joaquin Delta. DBW will concurrently be using mechanical harvesting to control spongeplant, water hyacinth, and water primrose infested areas as needed.

These aquatic invasive plants have no known natural controls in the west coast’s largest estuary, the Delta. Therefore, DBW operates “control” programs as opposed to “eradication” programs. It is likely that the plants will never be eradicated from the Delta. The division works with local, state and federal entities to better understand the plants, and implement new integrated strategic methods.

“DBW recognizes the impact of these aquatic invasive plants on people’s daily lives and businesses,” said DBW’s Deputy Director Lynn Sadler. “The good news is that this spring we received a little assistance from Mother Nature in terms of a deep frost and increased water runoff helping to flush the plants out to the ocean. Plus, we have more boats and more staff. Best of all we have local, state and federal partners who are helping us manage this challenge.”

New funding from the 2015/16 state budget and partnerships has increased the number of resources available to the division this year. Below is a list of these new resources and a summary of DBW’s 2016 herbicide treatment season:

Floating Aquatic Vegetation Control Program: Water Hyacinth and Spongeplant

Herbicide Control

  • Treatment Period:
    • Areas 2-4: Mar. 1, 2017 – Nov. 30, 2017 (south of Hwy 12)
    • Area 1: June 1, 2017 – Nov. 30, 2017 (north of Hwy 12) 
  • Potential Treatment Areas: Map Initially in and/or around, but not limited to the following areas: Fourteen Mile Slough, San Joaquin River, Empire Tract Slough, Middle River, Rock Slough, White Slough and Latham Slough.
  • Herbicides: Glyphosate, 2,4-D, or Imazamox (Herbicides are registered for aquatic use with the US Environmental Protection Agency and the California Department of Pesticide Regulation)

Mechanical Harvesting

  • Harvesting Sites:
    • January 2017 – April 2017
    • July 2017 – December 2017
  • Mechanical Harvesting Sites: Map Select areas of the Delta with high infestations or coverage of spongeplant, water primrose and/or water hyacinth, including the Stockton Waterfront and Port of Stockton.

Submersed Aquatic Vegetation Control Program: Egeria densa and Curly-leaf Pondweed

Herbicide Control

  • Treatment Period:
    • Starting March 1, 2017 through July 2017, treatment period based upon DBW field survey data, water temperatures and fishery surveys.
  • Potential Treatment Areas:  Map In and/or around the following areas (individual areas will be noticed prior to treatment application):
    • 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, Fourteen Mile Slough, Mosher Slough, Pixley Slough, Disappointment Slough, Bishop Cut, White Slough, and Honker Cut.
    • Sacramento Area: The Meadows, Cache Slough, Barker Slough, and Lindsey Slough.
  • Herbicide: Fluridone.

Mechanical Harvesting

  • This type of control method is not used for Egeria densa. That plant spreads by fragmentation. Cutting the plants back exacerbates the problem, as shreds of the plant float away and re-propagate.

Treated areas will be monitored weekly to ensure herbicide levels do not exceed allowable limits and that herbicide treatments have no adverse impacts on the environment, agriculture or public health in or near the planned treatment areas. All herbicides are registered for aquatic use with the U.S. Environmental Protection Agency and California Department of Pesticide Regulation. The public may view the public notices and sign up to receive weekly updates on this year’s treatment season on DBW’s website.

Last year’s treatment season was the most successful control year in the history of the California aquatic invasive plant control programs. The years 2015 and 2016 had the highest number on record for acres treated than any other year since the beginning of the water hyacinth control program in 1982. In 2015 DBW treated a total of 4,447 acres and in 2016 DBW treated 4296 acres. Also, aerial images were able to identify new water hyacinth nursery areas that this year DBW will be able to target in the early growth cycle of the plants. Infestation levels of Egeria densa were also greatly reduced.

The hard work performed during the 2016 season will serve as a benchmark to determine the geographical impact and spread of these aquatic invasive plants. Nevertheless, there are still certain regions of the Delta that are repeatedly, heavily impacted by the invasive plants. Sites with dead ends such as the Stockton Waterfront, tend to hold water hyacinth in the area longer due to no river flow, except tidal movements; west southwest and northwest winds, which prevail during spring, summer and fall season; and/or being close to big nursery areas. DBW hopes that treating the newly-identified nursery sites early in the season and using mechanical harvesting will significantly reduce infestation levels in dead end sites.

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 densacontrol program was authorized by law in 1997 and treatment began in 2001. In 2014, Spongeplant was authorized for control upon completion of the biological assessment and in 2015 curly-leaf pondweed was authorized under amendment to the Egeria densa control program.

Aquatic invasive plants negatively impacts Delta’s ecosystem as they displace native plants, block light needed for photosynthesis and reduce the amount of dissolved oxygen in the water. 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.

For more information, please visit the DBW aquatic invasive species website.


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.