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


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Photo: Ismail Niyax at Unsplash

The Division of Boating and Waterways (DBW) announced plans for this year’s control efforts for aquatic invasive plants in the Sacramento-San Joaquin Delta and its southern tributaries. Consistent with COVID-19 safety protocols, DBW personnel started herbicide treatments today to help control several invasive plants found in the Delta.


Treatment start dates and treatment sites may change depending on weather conditions, plant growth and movement, waterway traffic, location of sensitive species, presence of sensitive crops in adjacent lands, and other conditions.


“Invasive plants displace native plants in the Delta, create hazards for boaters and obstruct water ways and irrigation systems. DBW is putting technology and resources to work to limit these impacts,” said DBW’s Acting Deputy Director Ramona Fernandez. "We work collaboratively and in cooperation with the public and our local, state and federal partners who help us manage this challenge.”


The invasive plants include water hyacinth, South American spongeplant, Uruguay water primrose, Alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, hornwort (aka coontail), and fanwort.


Aquatic invasive plants have no known natural controls. Continued warm temperatures help the plants grow 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’s program works to control rather than eradicate the plants. The division works with local, state, and federal entities to better understand the plants and implement new integrated control strategies to increase efficacy. Public engagement is also key in DBW’s efforts.


All herbicides used in the program 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. The public may view the public notices, treatment area maps and sign up to receive weekly updates on this year’s treatment season and public opportunities on DBW's website.


Below is a list of proposed control actions for the 2021 treatment season.


Floating Aquatic Vegetation Control Program

Water hyacinth, South American spongeplant, Uruguay water primrose and alligator weed.

Herbicide Control

  • Treatment Period

  • Select Area 1 Sites and Areas 2-4: March 19, 2021 – Nov. 30, 2021

  • Note all Area 1 Sites: north of Hwy 12, Glyphosate and Imazamox are only being used.

  • Type of Herbicides: In areas 2-4 Glyphosate, 2,4-D, Diquat, 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, Fourteen Mile Slough, and Piper Slough.

Mechanical Harvesting (If necessary)

  • Harvesting Dates: March 2021 – April 2021 and July 2021 – Dec. 2021

  • 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

Brazilian Waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail/hornwort and fanwort.

Herbicide Control

  • Treatment Period: Starting March 19, 2021 through Nov. 30, 2021, 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, Korth’s Pirates Lair, New Hope Landing/Wimpy’s 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 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.


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


Last year, DBW treated 1,869 acres of floating aquatic vegetation and 2,056 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.


During the COVID-19 pandemic, DBW has provided training to staff to help reduce the risk of exposure to the virus while conducting treatments. As the state continues to issue guidance on preparing and protecting all Californians from the pandemic, the California Department of Parks and Recreation is monitoring the situation closely and is following guidance provided by the Governor’s Office and the California Department of Public Health, the Centers for Disease Control and Prevention, the Governor’s Office of Emergency Services, and local public health departments.


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 AIPs, and since then other plants such as Uruguay water primrose, Eurasian watermilfoil, Carolina fanwort, coontail/hornwort, and Alligator weed have been added to the AIPCP program.


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

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