Aquatic Pest Control
Cal Boatings ’s Aquatic Pest Control Program
- State legislation in 1982, designated Cal Boating as the lead agency for controlling Water Hyacinth in the Sacramento-San Joaquin Delta, its tributaries, and the Suisun Marsh.
- The Egeria Densa program was added in 1997; however, treatment did not begin until 2001 due to litigation that prevented all Cal Boating weed treatment during the 2000 season.
- Cal Boating currently spends approximately $6 million yearly on these efforts.
- These weeds have a negative impact on the Delta ecosystem. They displace native plants, block light needed for photosynthesis, reduce the amount of dissolved oxygen in the water, and deposit silt and organic matter at several times the normal rate.
- These weeds also have a significant impact on recreation and commercial activity in the Delta. They form dense mats of vegetation that create a safety hazard for boaters, obstructing navigation channels, marinas and irrigation systems.
- Due to the significant infestation, Cal Boating operates a “control” program as opposed to an “eradication” program. It is not expected that Water Hyacinth and Egeria Densa will ever be eradicated from the Delta area.
- The only successful control measure is herbicide application. Both plant species’ have no known natural enemies in the Delta environment. However, Cal Boating is studying the use of water hyacinth weevils as a biological control in Seven-Mile Slough.
- Cal Boating’s Aquatic Weed Control Program is permitted by the National Oceanic and Atmospheric Administration Fisheries, the U.S. Fish and Wildlife Service, and the Regional Water Resources Control Board.
- Cal Boating operates an extensive water quality monitoring program that shows that the control program meets water quality standards for herbicide use.
- Since litigation in 1999, treatment in most areas of the Delta has been limited to July 1 st through October 15 th due to regulatory agency concerns about endangered species. This restriction hampers program success as the herbicides must be applied during the early growth season to be most effective.
- Annual hyperspectral aerial survey is used to monitor changes in infestations over time.
Water Hyacinth (Eichhornia Crassipes)
- Water Hyacinth is an attractive floating aquatic plant with shiny green leaves and delicate lavender flowers.
- This extremely prolific aquatic weed can quickly become a dense floating mat of vegetation up to six feet thick.
- It grows faster than any other known plant, doubling in size every ten days in hot weather. It can potentially grow to cover 50,000 surface acres.
- It was introduced into the Delta from South America more than 100 years ago.
- The mats of floating plants can travel with river current and with tidal movement.
- Bethel Island in Contra Costa County is severely affected. Floating mats of Water Hyacinth catch on private docks and grow, oftentimes limiting boat access for residents.
Egeria Densa (Brazilian Elodea)
- Egeria Densa is a shallow-water submerged aquatic plant from Brazil that was introduced into the Delta 40 years ago.
- It is a popular aquarium plant, which may be how it entered the Delta.
- Egeria densa now infests approximately 6,000 surface acres, or twelve percent of the Delta.
- Egeria has spread at a rate of approximately 100 acres a year depending on environmental conditions. Egeria appears to grow more quickly in drought years and more slowly in years of heavy precipitation.
- Mechanical removal causes the plants to multiply, as new plants can develop from plant fragments.
- Rhode Island , an area of approximately 66 acres, is completely filled with Egeria Densa. Many parts of Franks Tract State Recreation Area, near Bethel Island, are seriously-affected.
