U.S. Joint Fire Science Program


Date of this Version


Document Type



Fire Science Brief, Issue 18, October 2008


US government work.


Noxious weeds are a serious problem that is spreading across the West. Herbicides such as Picloram have proven to be powerful tools in reducing weed invaders, although use of this tool has often produced unintended consequences. Broadleaf herbicides kill forbs, such as the noxious knapweed, but also harm native forbs such as arrowleaf balsamroot. Removing weedy forbs from a landscape creates opportunities for grasses to thrive—native as well as nonnative. Because of herbicide treatment, study sites experienced great increases in cheatgrass, a non-native grass of poor forage that also alters fire intensity and frequency. Managers should consider that efforts to reduce one problem plant may produce other problems.