Avoid driving through infestations and prevent livestock from overgrazing around infested areas. The stout taproot must be removed to a depth of several centimeters to prevent new shoot emergence. Tillage is effective but generally impractical for infested areas. Seed longevity is unknown and previously infested areas should be monitored for new seedlings for several years. There are currently no registered biocontrol agents for golden thistle.
Eradication is highly probable due to the small size of known infestations.
However, picloram is not currently labeled in California. Clopyralid is a selective broadleaf herbicide that controls many other thistles in the Asteraceae family, but has not been tested on golden thistle. Clopyralid is labeled for use on California rangeland, but may injure legumes. Dicamba, triclopyr, and 2,4-D may injure or kill other broadleaf plants. References Johnston, J. and Sonder, L. 1970.