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Division of Boating and Waterways to Tackle Aquatic Invasive Plants in Sacramento-San Joaquin Delta

The DBW estimates that its plan to combat aquatic invasive plants in the Sacramento-San Joaquin Delta will take the remainder of the year to complete.

California State Parks’ Division of Boating and Waterways (DBW) has unveiled its strategy to manage aquatic invasive plants in the Sacramento-San Joaquin Delta and its southern tributaries, the largest estuary on the West Coast.

From March 6 to Nov. 30, DBW crews will commence herbicide treatments targeting water hyacinth, South American spongeplant, Uruguay water primrose, Alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, ribbon weed and fanwort in the Delta. Depending on weather conditions and plant growth/movement, treatment schedules may be adjusted. Moreover, specific areas with significant water hyacinth infestations will undergo mechanical harvesting until December.

DBW collaborates with local, state and federal entities to understand these plants better and implement integrated control strategies. These aquatic invasive plants, lacking natural predators, disrupt the Delta’s ecosystem by displacing native flora. Favorable warm temperatures facilitate their rapid proliferation. Additionally, dense vegetation mats pose safety risks to boaters and obstruct navigation channels, marinas, and irrigation systems. These mats can also entangle boat propellers, leading to mechanical issues and potentially causing boats to become stuck or stranded. Additionally, some invasive plants can create safety hazards by reducing visibility on the water, making it harder for boaters to see obstacles or other vessels. Overall, invasive aquatic plants can impede boating activities and increase the risk of accidents or boat damage.

Due to their persistent spread, complete eradication from Delta waters is improbable. Hence, DBW operates a “control” program rather than an “eradication” program. Controlling invasive aquatic plants aims to minimize their impact on ecosystems and activities like boating and fishing. Methods include limiting reproduction and spread through removal, herbicides, biological controls and barriers. Eradicating them entirely is often impractical due to their resilience and spread, so management focuses on control for sustainable outcomes.

Deputy Director Ramona Fernandez expressed gratitude to the public and partners for their collaboration in combatting these invasive plants, emphasizing the collective effort to mitigate their impacts on Delta residents, workers and recreational users.

All herbicides utilized in DBW’s Aquatic Invasive Plant Control Program are approved for aquatic use by the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation.

Treated areas will be closely monitored to ensure herbicide levels remain within acceptable limits and adhere to EPA-registered label guidelines. Public notices and weekly updates on treatment progress for the current season are available on DBW’s website.

The following are the proposed control actions for the 2024 treatment season:

Floating Aquatic Vegetation

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

Herbicide Control

Proposed Treatment Period: March 6 – Nov. 30

Herbicides Used: Glyphosate, 2,4-D, Imazamox or Diquat

Potential Treatment Areas: San Joaquin River, Old River, Middle River, Fourteen Mile Slough, Snodgrass Slough, among others.

Mechanical Harvesting (If necessary)

Harvesting Dates: March-April, July-December

Mechanical Harvesting Sites: Areas with high water hyacinth infestations


Submersed Aquatic Vegetation

Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, ribbon weed and fanwort.

Herbicide Control

Treatment Period: March 6 – Nov. 30

Herbicides Used: Fluridone, Endothall or Diquat

Potential Treatment Areas: Anchorages, boat ramps, marinas and specific sites along Delta tributaries. 

Mechanical Harvesting

It is not applicable for submersed aquatic vegetation due to their propagation method.

To report sightings, receive program updates, or obtain further information on the control program, visit DBW’s website, contact via email at, or call (888) 326-2822.

In the previous year, DBW treated 2,377 acres of floating aquatic vegetation and 1,405 acres of submersed aquatic vegetation, without resorting to mechanical harvesting. Mechanical control methods used to manage invasive aquatic plants typically involve physically removing the plants from the water or disrupting their growth. A combination of herbicides and biological and mechanical control methods was employed to manage invasive plants at priority sites in the Delta.

Controlling invasive aquatic species in California is crucial to protect native ecosystems, maintain biodiversity and preserve the balance of natural habitats. Invasive species can outcompete native plants and animals for resources, disrupt ecosystem functions and alter habitats, leading to significant ecological and economic impacts. Additionally, invasive aquatic plants can obstruct waterways, hinder navigation and interfere with recreational activities such as boating and fishing by creating habitat alteration, competition for resources, altered water quality and habitat degradation. Controlling these species helps mitigate these negative effects and supports the overall health and sustainability of state aquatic environments.

In 1982, California state legislation designated DBW as the lead agency in controlling water hyacinth in the Delta, its tributaries, and the Suisun Marsh. The Egeria Densa Control Program was authorized in 1997, followed by spongeplant in 2012. Since 2013, DBW has expanded its jurisdiction to include other invasive aquatic plants such as Uruguay water primrose, Eurasian water milfoil, Carolina fanwort, coontail, Alligator weed and Ribbon weed. Funding for DBW’s Aquatic Invasive Plant Control Program is provided by revenues from boater registration fees and gasoline taxes.

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