Thursday March 5, 2026
California State Parks —
California State Parks’ Division of Boating and Waterways (DBW) announced today its plans for this year’s control efforts for invasive aquatic plants in the Sacramento-San Joaquin Delta and its southern tributaries (Delta). Starting March 19, DBW will start herbicide treatments on water hyacinth, South American spongeplant, Uruguay water primrose, Alligator weed, Brazilian waterweed, curlyleaf pondweed, Eurasian watermilfoil, coontail, fanwort and ribbon weed in the Delta. Treatment start dates may change depending on weather conditions and plant growth or movement.
These aquatic invasive plants have no known natural controls in the west coast’s largest estuary, the Delta. They negatively affect the Delta’s ecosystem as they displace native plants. 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. Due to their ability to rapidly spread to new areas, the plants will likely never be eradicated from Delta waters. Therefore, DBW operates “control” programs as opposed to “eradication” programs. The division works with local, state and federal entities to better understand the plants and implement new integrated control strategies to increase efficacy.