California to fight invasive plants in Sacramento-San Joaquin Delta with herbicide treatments

In its fight against invasive aquatic plants in the Sacramento-San Joaquin River Delta, the California State Parks’ Division of Boating and Waterways says it will begin a regiment of herbicide treatments that will last through the end of 2024.

Agency officials announced Wednesday that workers will start work on the Delta and its southern tributaries beginning March 6. The herbicide is meant to kill nonnative plants such as hyacinth, South American spongeplant, Uruguay water primrose, Alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, ribbon weed, and fanwort.

The process is expected to last through December, state parks officials said.

“These aquatic invasive plants have no known natural controls and negatively affect the Delta’s ecosystem as they displace native plants,” agency officials said in a news release. “Continued warm temperatures help the plants proliferate at high rates.”

In addition to portions of the Delta, officials said spraying would take place on the San Joaquin River, Old River and Middle River and at Fourteen Mile and Snodgrass sloughs.

Officials said they decided to spray the waterways because the flora is “known to form dense mats of vegetation creating safety hazards for boaters, obstructing navigation channels, marinas, and irrigation systems.”

The division is planning mechanical harvesting, if necessary, in addition to herbicide control, especially if hyacinth becomes overgrown.

Despite these efforts, officials conceded that the nonnative plants “will never be eradicated from Delta waters.”

The department said all herbicides used in the program are registered with the U.S. Environmental Protection Agency and the state’s Department of Pesticide Regulation. The work, officials said, would be done to ensure the process follows legal guidelines, including not exceeding allowable limits of herbicide use.

“Thank you to the public and partners for working with us on combating these aquatic invasive plants,” said Division of Boating and Waterways Deputy Director Ramona Fernandez. “Together we are mitigating their impacts on the lives of all who live, work, and recreate in the Delta.”