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Idaho enacts ring rot certification standards

Idaho Crop Improvement Association has implemented new certification requirements for bacterial ring rot.

By John O’Connell

Capital Press

Published on August 13, 2014 10:08AM

Potatoes display symptoms of ring rot, a disease which has flared up recently in parts of Idaho.

Submitted by Nora Olsen

Potatoes display symptoms of ring rot, a disease which has flared up recently in parts of Idaho.

IDAHO FALLS, Idaho — New Idaho Crop Improvement Association ring rot certification standards will require Idaho seed potato growers to collect tuber samples from seed lots beginning with this fall’s harvest.

Testing of at least 200 tuber samples will be required for the smallest seed lots and 400 samples from lots greater than a tenth of an acre.

The rules also require testing before any other lots on a farm can be sold to a commercial grower if there’s a possibility of contact with an infected lot, including from equipment or storage. Furthermore, growers who buy from a seed operation where an infection is found must test 4,400 tubers from those lots before planting them.

Ring rot detections will trigger a five-year probationary period, during which ICIA will swab the regulated farm’s facilities and equipment for bacteria before allowing new seed in, and the ring rot test sample will be increased to 1,200 tubers.

ICIA has long required the flushing of all seed potatoes from a farm after a discovery of the highly contagious and financially burdensome disease. Any lots containing ring rot can be sold only for an end use and can’t be replanted.

ICIA and the industry implemented the rules to address a ring rot flare-up that occurred in the state last season.

At the industry’s request, the Idaho State Department of Agriculture imposed its own temporary ring rot rule in the spring, requiring ring rot testing with a 400-tuber sample size of any Idaho spuds bound for export and mandatory reporting of any ring rot detections by both seed and commercial growers to help the agency trace the origin of infections. Based on discussions with the industry, Lloyd Knight, administrator of ISDA’s division of plant industries, said the rule will be revised to no longer mandate reporting by commercial growers, due to the challenge of conducting traces. ISDA will also defer to requirements of importers rather than requiring a ring rot test for exports. A final rule with those revisions is expected on Sept. 1.

“Folks were trying to avoid some redundancies between our program and ICIA,” Knight said. “Our (revised) rule recognizes there is now a certification process on seed that does require field inspections and lab analysis for ring rot.”

Knight said mandatory reporting will still be required by seed growers, and ISDA and ICIA will partner in tracing those ring rot cases.

ICIA’s test samples will consist of cores taken from the stem end of tubers. University of Idaho Extension seed potato pathologist Phil Nolte believes sequential testing of each seed generation should reduce the likelihood of bacteria slipping through the cracks. Nolte said Idaho’s new policy is unique in the U.S. and puts the state on par with requirements in Canada, though ICIA will use more sophisticated polymerase chain reaction testing.

Alan Westra, area manager of ICIA’s Idaho Falls office, said his staff learn signs of the disease by studying a small and isolated plot of infected plants. He said they’re now out inspecting fields, the vast majority of which are clean.

“The growers have stepped up and made these rule changes, and they’re pretty stringent,” Westra said.


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