9 Bacterial Ring Rot

In the fall of 2015 Bacterial ring rot was detected in a gardener's stored potatoes.

This is an extremely serious disease.  It is very important that the entire community acts at once as this can wipe out all of the potato crops in Northwest Territories. “ Dr. Stephen Brown University of Alaska.

Ring rot in potatoes

This disease is caused by the bacterium C. michiganensis

Once a crop or farm is infested with the bacterium, the disease will carry over from year to year and spread quickly. The bacteria can survive for 2 to 5 years in dried slime on the surface of machinery, crates, bins or burlap sacking, even if frozen. Volunteer potato plants and plant debris, including infected cull tubers will also carry the bacteria overwinter. The bacteria can be spread in rain and irrigation water and by insects, but wounds are needed for infection. Thus, the most important means of infection is cutting seed potatoes with contaminated knives. (Gov of BC)

The main points:

 1. Use only certified disease free seed potato each year. 

2. Good sanitation is crucial and everything that has come in contact with Ring Rot must be washed and disinfected. 

3. Don't plant potatoes in an infected area for at least one year. (Some sources have suggested 3- 5 years)

4. Infected potato, potato peals and plant debris should be burned, deep buried or put in the land fill. Do not put any of it in the compost.

Dr. Brown also gave the following details:

 -Any tools used around those infected potatoes should be washed in very hot soapy water and disinfected with a 10% bleach/water solution 9 parts water, 1 part bleach. (don't be tempted to use 100% bleach, it is less effective.)

-Everything that has come in contact (knives, cutting boards, shoes, etc.) has got to be cleaned and disinfected.  Bacterial Ring Rot's survival strategy is in the slime it produces.  When it dries on the surface of a tool, it can survive for up to 5 years and be infecting everything which comes in contact.

-It's almost certain you got BRR by cutting seed potatoes.  Knives should be disinfected in 10% bleach/water in between every cut.  It is speculated that there was not BRR in North America until the potato industry starting cutting seed potatoes in the 1930's.  In my own garden I do not cut seed potatoes.

-It is crucial certified disease free seed be used each year.

-Burning is good idea, but they can go in the landfill too.(but not the compost)”

A few points from our situation here on Latham Island in 2015:

 ·         Luckily, we have our own garden so don’t have shared tools.

·         We planted three varieties of spud this year and it is only the Organic Goldrush that seem to be affected (others were Kennebec and Norland).

·         We harvested the crop in October and I didn’t notice any problems then. In retrospect, I think that some potatoes we used earlier might have had a brown ring just inside the skin, which is an early sign, I’ve now learned. 

·         The ones pictured are more advanced.  Some of the white areas inside the ring are revoltingly slimy.

·         What first alerted me was a slight smell, sweetish and unpleasant, when I went to get some from storage about a week ago.

·         From a crop of about two full milk crates, we’ve had around a dozen bad potatoes.

·         I am keeping a close eye on the potatoes in storage.  Since finding the first lot, I’ve come across one more.  

Selected references:
http://www.agf.gov.bc.ca/cropprot/brr.htm BC Government information page

Thank you to Ruth Bowen and Jade Cambron for gathering this information. Ruth is not a community gardener and these particular potatoes were not grown in the community garden. She has generously shared the information and as a public service the collective is providing a space to share it. This is a reminder to us that although we are relatively isolated and have few pests and diseases affecting our crops, we must still practice safe gardening techniques.

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