Lower Columbia River Watershed Council

Blackberry Rust Fungus Found in Columbia County West of Clatskanie

by Cyndi Edmonds

A species of rust fungus confirmed in Himalayan blackberry plants along the southern Oregon coast this spring has now been found in Columbia County.
Margaret Magruder, coordinator of the Lower Columbia Watershed Council, a Clatskanie rancher and former member of the state board of agriculture, and Glenn Miller of the Oregon Department of Agriculture (ODA), identified the fungus in the Marshland area west of Clatskanie Monday afternoon.
In addition to infecting the unwanted, weedy species of blackberry, Phragmidium violaceum has been found on evergreen blackberry, a commercial variety common in Oregon, although it does not seem to impact Oregon’s small, wild blackberries. Prior to this year, the rust had never been officially confirmed in North America.
Miller said it was too early to tell whether the rust fungus is ultimately good or bad for Oregon, although it might cause the death of favorite local blackberry patches.
In addition to Columbia County, positive confirmation of P. violaceum has been made in Coos, Curry, Douglas, Lincoln, Clackamas, Multnomah and Marion county blackberries. Only in Clackamas, Multnomah and Marion counties has the rust affected evergreen blackberry bushes.
There is no evidence at this time that P. violaceum affects Oregon’s most valuable commercial blackberry species including Marionberry, Boysenberry and Loganberry. Officials say it is too early to determine the impact of the rust on Oregon’s $30 million industry.
ODA has established an ongoing monitoring and sampling program that includes blackberry species in 18 western Oregon counties. Officials hope to learn more about the geographic distribution of P. violaceum and how prevalent it is within Oregon blackberries.
In addition, ODA is working with the U.S. Department of Agriculture’s Animal Plant Health and Inspection Service (APHIS), USDA’s Agricultural Research Service (ARS), Oregon State University and the Oregon Raspberry and Blackberry Commission on identifying effective management strategies, including use of fungicides, to control blackberry rust in the future.
The origin of the rust is unknown. Used as a biological control agent for unwanted blackberry species in Australia, New Zealand and Chile, the rust was considered by ODA and USDA in the past for possible introduction to North America for control of the weedy variety of blackberry. However, all potential biocontrol agents must go through a strict series of protocols before environmental release. ODA and USDA were still in the discussion stage when the pathogen was first discovered in Oregon.
To identify blackberries infected by the fungus, look for patches beginning to yellow, Miller said. P. violaceum leaves purple spots on the top of the leaves of Himalayan blackberry with corresponding yellow and black pustules underneath the leaves. The rust reduces the plants’ vigor. As it develops, there can be some die-back of the cane.
Downloadable images of blackberry rust can be found online at: http://oregon.gov/ODA/ PLANT/gallery_bbr.shtml.
For more information, contact Dan Hilburn at 503 986-4663.

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