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Posted 26 October 2012. PMN Crop News.

Potato Growers Urged to Take Aggressive Action to Control Bacterial Ring Rot Flare-up

Source: University of Idaho Press Release.

Idaho Falls, Idaho (October 1, 2012)--College of Agricultural and Life Sciences potato experts at the University of Idaho are reviving a task force to help growers address a flare-up of bacterial ring rot disease.


Phillip Nolte, a University of Idaho Extension seed potato specialist at Idaho Falls, said the disease is reaching levels not seen in a decade. Mainly a threat to the appearance and storage of potatoes, bacterial ring rot is not associated with any human health concerns.

“It’s a cyclic thing. We last saw problems with it in 2002, and there was an earlier flare up in the mid-1990s,” Nolte said.

Growers then controlled the disease and largely eliminated it by stepping up their sanitation practices while cutting seed during spring planting and thoroughly cleaning and disinfecting all equipment and storages between crops,", Nolte said.

The same practices will control the current outbreak, Nolte said. The task force will help the potato industry, state and University of Idaho experts help growers tackle the disease and prevent the problem from becoming worse, said Nolte, who will lead the group.

Early monitoring shows that infection rates are heavy in some fields, but more monitoring is needed to determine the regional impact. Harvest will provide the most detailed information on the extent of the disease.

In cases where monitoring shows a significant problem with bacterial ring rot, Nolte said, growers will want to delay harvesting those fields until last. That’s because infected potatoes will rot in the soil and fewer will have to be sorted out before storage.

The cyclic nature of bacterial ring rot’s appearance has much to do with relaxed vigilance by both seed potato producers and commercial growers, Nolte said. “After it appears, everyone is very aware and aggressive in their sanitation programs. Then we don’t see bacterial ring rot for several years and people get complacent.”

The bacterial disease is spread to healthy tubers when a contaminated tuber leaves bacterial inoculum on potato seed cutting and handling equipment. Bacterial ring rot can remain viable in dried bacterial slime and in dried potato sap on equipment and storage surfaces for many years if they are not properly disinfected. The disease also can infect tubers but cause no symptoms, which is what makes it so difficult to prevent unless all recommended sanitation practices are aggressively followed, Nolte said.

In a publication, “Guidelines for Recognizing and Managing Bacterial Ring Rot of Potato,” prepared for growers, Nolte and Nora Olsen, a potato storage expert at the Kimberly/Twin Falls Research and Extension Center, offer cleaning and disinfection recommendations. A copy of this guide is available upon request via email from either Nolte at or Olsen at

Nolte and Olsen warn growers to take the recommendations seriously: “There are no shortcuts when dealing with BRR, the approach to eliminating this disease must be aggressive and thorough and involves sanitation practices that go far beyond what is considered to be normal clean up procedures.”

On any seed potato seed farm where the disease has been detected, Nolte recommends testing seed potatoes for BRR if they were not directly linked to diseased lots. If there is any risk that a lot was exposed to the disease it should not be used as seed.

A thorough cleaning of all potato handling equipment from harvesting to transportation and storage must be performed on all seed and commercial potato farming operations.

The next step, disinfection, requires three steps: removal of all potato debris and contaminants, washing all newly cleaned surfaces with hot water and detergent and then application of a disinfectant solution to all surfaces.

Editor’s Note: The Plant Management Network has produced a webcast on Bacterial Ring Rot. View Bacterial Ring Rot Talk