UPDATE: Blue-green Algae FAQS

Aquatic Weeds


In 1982, California state legislation designated the Division of Boating and Waterways (DBW) as the lead state agency to cooperate with other state, local and federal agencies in controlling Water Hyacinth in the Sacramento-San Joaquin Delta (Delta), its tributaries, and the Suisun Marsh. The Egeria Densa control program was authorized by law in 1997 and treatment began in 2001. The importance of both control programs is evident in that Water Hyacinth and Egeria Densa have a negative impact on the Delta's ecosystem as they displace native plants, block light needed for photosynthesis, reduce the amount of dissolved oxygen in the water, and deposit silt and organic matter several times the normal rate. Both aquatic invasive weeds are known to form dense mats of vegetation creating safety hazards for boaters, obstructing navigation channels, marinas and irrigation systems.

Egeria Densa

Egeria densa (Brazilian Elodea) is a shallow-water submerged aquatic plant from Brazil, popularly used as an aquarium accessory that was introduced into the Sacramento-San Joaquin Delta about 40 years ago (possibly from use in home aquariums). Egeria densa and other submerged vegetation now infest many thousands of surface acres of the Sacramento-San Joaquin Delta. The plant can spread very quickly depending on environmental conditions, often by fragmentation. The Department of Boating and Waterways (DBW) is the only entity authorized to treat Egeria densa in California with herbicides.

Water Hyacinth

Water Hyacinth is an attractive floating aquatic plant with shiny green leaves and delicate lavender flowers. It was introduced into the Delta from South America more than 100 years ago. This extremely prolific aquatic invasive plant can double in size every ten days in hot weather and can quickly become a dense floating mat of vegetation up to six feet thick. The mats can travel with river currents and with tidal movement. Mats can also attach to structures in the water, limiting access to boats and reducing swimming areas.

What Can You Do To Reduce Aquatic Plants and Weeds?

Pull and properly dispose of aquatic plants and weeds! Here’s how:

  1. Pull the plants and weeds from their roots. Remove the entire plant/weed, including the roots.
  2. Place the entire plant/weed in garbage bags or cans and move them far away from the water. If plants/weeds are left to dry on the dock or near the water line, seeds will blow back into the water and cause more growth.
  3. Encourage your friends and neighbors to properly remove and dispose of aquatic plants/weeds near their property.
  4. Avoid any contamination of our waterways. All spraying MUST be done by a licensed pesticide applicator. This is required under the Clean Water and Endangered Species Acts.