Water Hyacinth

Water Hyacinth is an extremely prolific aquatic invasive plant that can double in size every ten days in hot weather according to the CA State Parks, Division of Boating and Waterways. 

With summer just around the corner and the boating season about to get underway, the California Department of Parks and Recreation’s Division of Boating and Waterways (DBW) has started its annual treatment of Delta waterways for aquatic invasive species (AIS), like the ubiquitous water hyacinth.

DBW is charged with managing AIS, and their treatment season begins in March, running through November. Treatment areas encompass a number of East County locations, including Discovery Bay, Big Break, Piper Slough, Taylor Slough and Cruiser Haven Marina.

With no natural controls, invasive species can grow unchecked, creating a variety of environmental concerns. In addition to inhibiting navigation, they can crowd out native plants, damage fish habitat and block agricultural and municipal water intakes.

“We take our responsibility seriously to control aquatic invasive plants in the Delta, while at the same time protecting the environment, agriculture, public health and water quality,” said DBW’s acting Deputy Director Ramona Fernandez in a press release. “To minimize impacts from our use of herbicides, we continue to leverage technology and resources through collaboration and cooperation with the public and our local, state and federal partners who are helping us manage this challenge.”

Aquatic invasive plants are characterized as either submersed aquatic vegetation (SAV) or floating aquatic vegetation (FAV). Brazilian waterweed, curly-leaf pondweed, Eurasian watermilfoil, coontail and fanwort are examples of SAV and are targeted for treatment with herbicides, primarily fluridone, sold commercially in products like Sonar.

Water hyacinth, South American spongeplant and Uruguay water-primrose are examples of FAV commonly found in the Delta, and they can be seen growing in thick mats on the surface of the shallow, slow-moving bodies of water. In addition to treatment with herbicides like glyphosate, sold commercially in products like Roundup, FAV can be mechanically harvested, hand-picked or even treated using biological controls such as water hyacinth weevils — insects that feed exclusively on their namesake plants.

In a press release, DBW stated that the application of herbicides to control AIS adheres to regulatory requirements and protocols. A water quality monitoring program is carried out by DBW to ensure compliance with all water quality standards, including drinking water standards. The planned use of herbicides is reviewed by a variety of federal, state and local agencies such as the U.S. Fish and Wildlife Service and county regulators.

“The county agricultural commissioner’s role with DBW is a regulatory one,” said Matthew Slattengren, Contra Costa County agricultural commissioner. “... Rules and regulations are in place along with a system for registering pesticides with DPR (Department of Pesticide Regulation) before use in California, including scientific studies to help ensure safety of applicators, the public and the environment.”

The year’s SAV treatment plan calls for herbicidal treatment of 2,841 acres, much less than last year’s 4,256 acres. One parcel that is not slated for treatment this year is Franks Tract, a popular spot for boaters, fishermen and waterfowl hunters.

“It makes no sense to ignore the weed issue in Franks Tract, which is absolutely not under control,” said Jamie Bolt, harbormaster at Bethel Harbor.

However, in a conference call with The Press, Edward Hard, chief environmental program manager with DBW, stated that sites managed by DBW won’t be treated for more than three consecutive years.

“Last year was the last year of a three-year cycle for Franks (Tract),” explained Hard. “Franks sticks out in large part because, if you go by our sites — we have over 400 sites and 101,000 acres that we have jurisdiction over — that is the largest site. On a given year, that would have a big impact.”

Hard went on to say that the inclusion of Franks Tract, or any other parcel, in future treatment plans is determined by visual observation, photographic evidence and hydro acoustic testing to determine the type and density of plant growth.

“We will be going out and mapping Franks in anticipation that 2020 would be the start of a new cycle,” said Hard. “That’s dependent on whether or not we find large areas of vegetation of the right type that we’re authorized to control”

DBW is authorized to treat up to 4,500 acres of FAV in 2019. Last year, they treated approximately 2,300 acres across 150 sites.

“It is impossible to predict exactly how much acreage will be treated,” said Gloria Sandoval, DBW deputy director of public affairs. “Floating aquatic vegetation fluctuates dramatically, depending on weather and spring runoff conditions.”

Though the herbicides used in the treatment of invasive aquatic plants are considered safe if used properly, DBW advises people to avoid areas that are in the process of being treated and to follow the direction of the technicians applying the treatment.

For more information about DBW’s aquatic plant control program, visit: dbw.parks.ca.gov/?page_id=28764

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