When you cut through a tuber infected with ring rot, classic internal symptoms are visible.
When you cut through a tuber infected with ring rot, classic internal symptoms are visible.

Bacterial ring rot, a cyclic problem of stored potatoes, has flared up again this season in Idaho.

As a result, the University of Idaho is reviving its task force to help growers deal with the problem, according to a news release.

Caused by Clavibacter michiganensesubsp. sepedonicus, ring rot causes vascular breakdown within the tuber, but it's not a human health concern.

Before this season, the last flare-up in Idaho was in 2002.

Growers were able to manage and largely eliminate the problem by implementing sanitation practices during seed cutting in the spring.

They also thoroughly cleaned and disinfected all equipment and storage facilities between crops.

The same practices should control the current outbreak, according to Phil Nolte, a University of Idaho Extension seed potato specialist at Idaho Falls.

Early monitoring shows the problem is variable, hitting some fields harder than others.

More monitoring will be conducted as harvest progresses to determine the extent of the disease.

In fields with a heavy outbreak, growers should try to delay harvest to allow infected potatoes to rot in the field so fewer will need to be sorted out before storage.

The bacterial disease is spread when an infected tuber comes in contact with a piece of equipment, including cutting knives, handling machinery or storage surfaces.

The bacteria is then transferred onto the surface, where it can infect other tubers that contact it.

The disease also can infect tubers but not cause symptoms.

Much like Typhoid Mary, these symptomless tubers can spread the disease.

Nolte and Nora Olsen, a potato storage expert at the Kimberly research center, have written a publication, “Guidelines for Recognizing and Managing Bacterial Ring Rot of Potato.”

It is available upon request by e-mailing Nolte or Olsen.