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Yellow Starthistle Mapping Project: Program Details
Background & Problem
Yellow starthistle (Centaurea solstitialis) is estimated by the California Department of Food and Agriculture to cover over 12 million acres in California. It is toxic to horses and is avoided by most grazers once it has bolted and become spiny. It is a serious nuisance on recreational lands and degrades the resale value of private property. It increases fire danger and poses a major threat to biodiversity in native ecosystems. Yellow starthistle (YST) is completely beyond total statewide eradication. Such a project would cost billions of dollars and engage tens of thousands of people for many years. Currently, the major activity devoted towards YST is focused on reducing infestation levels in areas where YST is very abundant. However, YST is still moving into non-infested watersheds. There are large areas, including private land and public forests and parks, that can still be protected from the presence of YST in whole watersheds and valleys. While its method of spread has not been documented conclusively, it is widely believed that YST moves down transportation corridors or is spread in jumps by movement of contaminated feed, equipment, fill, et cetera. In areas like the mid-elevation western Sierra Nevada slope, control efforts should focus on prevention of further spread and on local eradication. Agencies and private landowners need better information on where to prioritize this type of control and eradication so that they are making the most effective use of their budgets. Research and implementation of biological control is the best hope for a long term permanent control strategy. However, we cannot allow the unrestricted spread of YST further into the Sierras while we wait with uncertainty for a biocontrol silver bullet.
Solution
The California Department of Food and Agriculture and CALTRANS, with support from the County Agricultural Commissioners, members of the California Interagency Noxious Weed Coordinating Committee and local Weed Management Areas, propose to initiate a cooperative yellow starthistle mapping and assessment project. This project will involve the mapping of YST by a few hundred resource management professionals, qualified amateurs and landowners. Mapping will be carried out at a fairly high level of resolution and the collation of this information will be put into a Geographic Information System (GIS). Primary areas of focus will include public lands and roadway easements. A secondary focus will be on the mapping of YST on private land. Private land mapping will be coordinated specifically at the local level and will only show up in the GIS as section (sq. mile) general locations. Upon completion of the mapping project, private lands will only be mapped at high resolution with the landowner’s approval and consent.
An eastern boundary of YST spread will be established. To the best of everyone’s knowledge, YST will not be known to occur east of this boundary. Immediately west of this boundary, a containment zone will be determined and key eastward outlier populations (EOPs) will be identified. Yellow starthistle in the containment zone and EOPs will be targeted as having high eradication and control priorities. When feasible, the containment zone could be a "knock-back zone" where concerted efforts are made to move the eastern boundary westward through local eradication. As part of the assessment phase, potentially infestable areas (where YST can biologically survive) will be biologically determined and mapped to focus detection and emphasize the importance of the prevention efforts. If successful, this project will serve as a pilot for similar YST and invasive weed control mapping/assessment projects throughout the state.
Click here to read a poem about thistles
Contact Information
Program Manager: Terrance Lorick
E-mail: tlorick@cdfa.ca.gov
Phone: (916) 651-0573
E-mail: weedmapper@cdfa.ca.gov
Phone: (916) 654-0768