Arundo Control and Restoration Project

Giant reed (Arundo donax) plants growing in the Sacramento-San Joaquin Delta. — Giant reed (Arundo donax)

Arundo (Arundo donax) is a non-native invasive grass that grows up to 25 feet tall along the edges of sloughs and canals in the Sacramento-San Joaquin Delta, and is also abundant in the Sacramento and San Joaquin River watersheds. Arundo restricts shoreline access, consumes larger quantities of water than native vegetation, obstructs flood control channels, creates fire hazards along sloughs and rivers, and displaces native plants and associated wildlife.

The Delta Conservancy and the Department of Water Resources (DWR) identified the need to address Arundo in the Delta and to restore the areas overrun by the grass with native vegetation. The Delta Conservancy established the Arundo Control and Restoration Project first to map and prioritize areas of Arundo in the legal Delta, and then to control Arundo and restore native habitat.

With funding from the Department of Water Resources, the Delta Conservancy is working with the Sonoma Ecology Center to map Arundo sites in the Delta and prioritize those sites according to their restoration value.

Also with DWR funding, the Delta Conservancy is contracting with the Solano Resource Conservation District and Sonoma Ecology Center on a pilot project of Arundo control and habitat restoration in the Cache Slough Complex. Implementation of this project has been ongoing since 2015 and will be followed by three years of maintenance and monitoring.

Sonoma Ecology Center and Solano Resource Conservation Districts have been working since 2015 with private landowners in Cache Slough Complex to treat and monitor Arundo. Overall, they have assessed more than nine miles of Cache Slough shoreline and treated any Arundo patches present. In 2016, Sonoma Ecology Center re-surveyed approximately five miles of shoreline initially addressed in 2015, and treated any Arundo re-growth.

Solano Resource Conservation District has installed one two-acre restoration project and is actively monitoring and maintaining it in cooperation with the landowner. For the second 15-acre restoration project, all permits have been obtained and active restoration will soon begin.

The Delta Conservancy is also working with the U.S. Department of Agriculture – Agricultural Research Service’s Delta Region Areawide Aquatic Weed Project (web link) in identifying potential sites for biological control of Arundo.

A map of the Sacramento-San Joaquin Legal Delta, located in Northern California, showing locations of Arundo donax infestations in this region color-coded to represent each location’s suggested eradication priority. The Sacramento-San Joaquin Legal Delta contains areas in Yolo County, Solano County, Sacramento County, San Joaquin County, Contra Costa County and Alameda County. The northern border of the Legal Delta extends to the city of West Sacramento and the Interstate 80 freeway in Yolo County. The western border extends past California State Route 113 in Solano County, and past the cities of Antioch and Brentwood in Contra Costa County. The southern border of the Legal Delta extends past the city of Tracy in southern San Joaquin County. The eastern border extends to the city of Stockton in San Joaquin County and to the Interstate 5 freeway in Sacramento County. The map shows infestations of Arundo donax within the legal Delta. The highest concentrations are in the Cache Slough Complex and along the Sacramento River downstream of Cache Slough. Most infested sites in this region are considered high priority for eradication. Arundo also has a high density along some of the main waterways in the central and southern portions of the Delta, including long stretches of the Old, Middle and San Joaquin rivers; but fewer sites in these areas are considered high priority for eradication. The northern and northeastern portions of the Delta harbor fewer arundo infestations than the central, western, and southern portions.

Click the image above to view the full map of Arundo donax sites in the Delta.

Websites for Arundo Control and Restoration Project Partners:

Chemical treatment of Arundo on a levee bank using an aerial boom lift. Photo by Sonoma Ecology Center. — Chemical treatment of Arundo
(Photo by Sonoma Ecology Center)

Arundo patches on the backshore of a slough within Cache Slough Complex. — Arundo within Cache Slough Complex

Chemically treated Arundo on the left, residual riparian vegetation on the right

Close-up picture of a tiny black arundo wasp with red eyes on a green arundo shoot. Photo by USDA-ARS. — Two Arundo biological control agents being introduced by USDA (Arundo wasp) (Photo by USDA-ARS)

Recent plantings and an irrigation line at a restoration site. Photo by Solano Resource Conservation District. — First Arundo restoration site in October 2016
(Photo by Solano Resource Conservation District)