Arundo and Tamarix Eradication Project

Background

Arundo donax (Giant Reed) and Tamarix ssp (Tamarisk or Salt Cedar) are invasive plants that cause significant environmental and economic losses in California and elsewhere. Arundo is very flammable and, because it is shallow-rooted and top-heavy, causes bank erosion when its roots are undercut by stream action and the plants fall over, taking the bank with them. Tamarix out-competes native plants due to its intensive water use and the salts that it exudes, which change the soil chemistry. Millions of dollars are spent annually to try to control or eradicate these two invasive plant species.

This eradication project was funded by a grant from the CalFed Bay-Delta Authority. It included 8 partners in various watersheds in Northern and Central California, led by Team Arundo del Norte (TAdN) . This was a 3-year grant which was to end in March 2009, but extended to March 2010 due to a 9-month state freeze on funding in 2009.

Project Description

Our project area was the entire length of Lindo Channel and Big Chico Creek upstream of the diversion dam at Five Mile Recreation Area. All of the Arundo and Tamarix occurrences in this area were surveyed. 219 Arundo locations and 23 Tamarix locations were mapped using the TAdN GeoWeed database protocols. The "mother plant", or original source of the infestation, was just upstream of the bridge at the Bidwell Park Golf Course. Since Arundo in California propagates only by rhizomes and nodes of the cane breaking off and floating downstream, eliminating the upstreammost occurrences was essential to the success of the project.

Within the project area (which did not include Big Chico Creek downstream of Five Mile), all of the Big Chico Creek Arundo was within city-owned Bidwell Park. Much of the Lindo Channel Arundo and Tamarix were also on city-owned property, but some of these infestations were on private property and some on land owned by the County of Butte. The goal was to eradicate all Arundo on both public and private property, as Arundo left untreated can re-infest downstream properties.  However, because this was a voluntary program, landowner permission was required for any treatments on private property. The majority of landowners did allow treatment of Arundo on their properties.

Property owners adjacent to Lindo Channel (about 350) received a letter about the project and a brochure describing the problems associated with Arundo donax. Two community meetings were held to answer stakeholder questions about the need for the project, the treatment methods that would be used and the project schedule. A similar presentation was made to the Bidwell Park and Playground Commission.

Treatments and Results

The Arundo and Tamarix plants were treated in the fall with a foliar application of aquatic formulations of glyphosate and (in most locations) imazapyr herbicides. In some areas, these treatments were provided by project's eradication contractor and in others by the Bidwell Park maintenance staff. For much of the Arundo, a single treatment was sufficient to eliminate the Arundo clump. For some of the larger areas of infestation and for plants that had previously been cut down (thus providing less surface area for the herbicide to penetrate), additional treatments were required in subsequent years. The fourth and fiinal treatment to the remaining plants for which permission was granted to eradicate took place in the late summer and early fall of 2009. Follow-up monitoring and possible re-treatments will be required for several years to ensure that all upstream infestations have been eliminated. The City of Chico will provide this monitoring and re-treatment, as needed, for any remaining Arundo on city-owned property.