Phragmidium violaceum, a rust species new to North America, has reportedly been found along the southern coast of Oregon impacting weedy Himalayan blackberry plants. This rust is used for biocontrol of invasive blackberry in Australia, New Zealand, and Chile; where research has shown it to have a very narrow host range of specific weedy blackberry species. Research is underway to confirm Oregon’s commercially produced and native blackberry varieties are not susceptible. Fungicides are available if desirable blackberries varieties are found susceptible. Currently, the rust is limited to the southern coast of Oregon in Coos and Curry Counties. Identification of this particular rust is difficult and can easily be confused with other blackberry diseases.
For more information and photos, visit the Oregon Dept. of Ag. website: