For Immediate Release: 3/8/2016

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



Gloria Sandoval

Deputy Director of Public Affairs

(916) 651-7661


Sacramento, Calif. -- California State Parks Division of Boating and Waterways (DBW) will begin herbicide treatment of water hyacinth and Egeria densa this Thursday, March 10, in various areas of the Sacramento-San Joaquin Delta (Delta). DBW will simultaneously be treating curly-leaf pondweed and Spongeplant, and using mechanical harvesting to control water hyacinth infested areas as needed.

These aquatic invasive plants have no known natural controls in the west coast’s largest estuary, the Delta. Seed production from water hyacinth has established a high seed bank in the sediment. Seeds will continue to germinate even if all surface plants have been removed from the water. Due to this and their ability to rapidly spread to new areas, it is likely that the plants will never be eradicated from Delta waters. Therefore, DBW operates “control” programs as opposed to “eradication” programs to mitigate the impacts of these invasive plants. The division works with local, state and federal entities to better understand the plants, and implement new integrated strategic methods.

“The Division of Boating and Waterways 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 winter 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 2014/15 state budget and continued partnerships has increased the number of resources available to the division this year. Below is a list of these resources and a summary of DBW’s 2016 herbicide treatment season:

New Resources

  • Seven new DBW field technicians and two field managers.
  • Up to six California Conservation Corps members. They will be assisting DBW with controlling water hyacinth via boat or via docks to aid mechanical harvesting operations (when needed).
  • New prop motors for six aging boats.
  • Four new boats are being built.
  • Four new trucks.

Floating Aquatic Vegetation Control Program: Water Hyacinth and Spongeplant

Herbicide Control

  • Treatment Dates: Map
    • Areas 2-4: Mar. 10, 2016 – Nov. 30, 2016
    • Area 1: June 1, 2016 – Nov. 30, 2016


  • Treatment Areas: Initially in and/or around, but not limited to, the following areas: Fourteen Mile Slough, Middle River, Old River, Paradise Cut, Whiskey Slough, San Joaquin and Tuolumne rivers, including the Stockton Waterfront and Port of Stockton.


  • Herbicides: Glyphosate, 2,4-D, Imazamox or Penoxsulam.


Mechanical Harvesting

  • Treatment Dates
    • January 2016 – April 2016
    • July 2016 – December 2016


  • Treatment Areas: Select areas of the Delta with high infestations or coverage of water hyacinth and/or spongeplant, 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 10, 2016 through July 2016, treatment period based upon DBW field survey data, water temperatures and fishery surveys.


  • Treatment Areas: In and/or around the following areas (individual areas will be noticed prior to treatment application):
    • Anchorages, Boat Ramps and Marinas: Brannan Island State Recreation Area, Cruise Haven, Ox Bow Marina, Owl Harbor, Buckley Cove and Near Old River: Franks Tract (partial); Discovery Bay West; Holland River-side; and Rock and Piper sloughs.
    • Stockton Area: Hog Island (Power Squadron), Little Potato Slough (Tower Park Marina and Grindstone Joe’s), Tinsley Island (St. Francis Yacht Club) and Fourteen Mile Slough (including Village West Marina).
    • Sacramento Area: Sycamore and Beaver sloughs.


  • Herbicide: Fluridone.

Mechanical Harvesting

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

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 aquatic invasive plant control programs. More acres were 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 compared to 2,617 in 2014. Also, aerial images were able to identify new water hyacinth nursery areas that DBW will be able to target this year during the early growth cycle of the plants. Infestation levels of Egeria densa were also greatly reduced. For example, in Discovery Bay infestation of the plants was greatly reduced compared to 2014 levels, as evidenced by mapping surveys.

The hard work performed during the 2015 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 a lack of river flow, winds and/or being close to water hyacinth nursery sites. 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.

Aquatic invasive plants negatively impact the 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.

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.

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.

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