Officials Anticipate More Ring Rot Testing in Seed

Published online: Dec 06, 2013 Seed Potatoes John O'Connell, Capital Press
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Potato industry officials anticipate much greater interest in winter testing of seed for bacterial ring rot, based on another flare-up of the disease in 2013.

The Idaho Crop Improvement Association began offering highly accurate polymerase chain reaction testing for ring rot this spring after the disease resurfaced as a problem in the 2012 crop following a long absence.

Oregon State University recently announced it will also offer PCR testing for ring rot in Hermiston, Ore., and University of Idaho Extension potato seed pathologist Phil Nolte said UI is looking at adding another PCR lab in the vicinity of Moscow and Pullman, Wash.

"The way out of the woods right now is for there to be testing on these seed lots," Nolte said, predicting that the combination of heightened voluntary testing and improved grower sanitation practices will result in a reduction in ring rot next season.

Ring rot, first reported in the U.S. in the 1930s, can be spread by seed and equipment such as seed cutters and truck beds. Symptoms aren't always visible but may include wilted foliage, tuber cracking, bacterial ooze and destruction of the vascular ring.

Ring rot is a zero-tolerance disease, meaning a single positive plant in a field is cause for rejection of a seed lot. In Idaho, detection also prevents growers from re-certifying seed from any other lots, forcing them to start with new seed after cleaning equipment and buildings.

Nolte said ring rot was scheduled as a discussion topic for the certification section of the Potato Association of America meeting, which started Dec. 2.

Commercial potato grower Dan Moss of Rupert, Idaho, chairman of the Idaho Potato Commission, believes it may be time for the state to mandate ring rot testing in seed.

"What we're doing right now isn't working," Moss said. "I think if the potatoes are going to be re-certified, we need to change the rules, and it needs to all be tested."

Moss said IPC is funding more research into ring rot and has been facilitating meetings involving the Idaho State Department of Agriculture, seed growers and UI to consider options. Moss believes the major processors may eventually require their commercial growers to avoid seed that hasn't been ring rot tested.

"I would absolutely want my seed PCR tested this year," said Dan Hargraves, executive director with Southern Idaho Potato Cooperative.

Hargraves acknowledged the state's infrastructure is inadequate to test every seed lot. 

Doug Boze, executive vice president of the Idaho Crop Improvement Association, said Lamb Weston has recommended that its growers test their product before delivery.

"I would probably think there's going to be more voluntary testing," Boze said.

Since it opened last spring, Boze said his lab has PCR tested 300 sets of 200 tuber samples and has another 200 sets awaiting testing. Boze, however, believes mandating ring rot testing as a certification requirement would be a "drastic rule change."

"The expense to the grower would be phenomenal," Boze said. "I don't believe growers and the industry are at a point in time where they want to impose additional certification standards."

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