In addition to Dickeya dianthicola being found in potato fields in New Jersey, the pathogen has also been detected in fields from Long Island to Florida this summer. To date using PCR test results and North American Certified Seed Potato Health Certificates to track Lot No., the pathogen has been detected in 12 states (DE, FL, MD, MA, NJ, NY, NC, PA, RI, VA, WV, and OH). Potato growers, crop consultants, and Extension personnel in states which grow potatoes from Maine or New Brunswick, Canada should remain vigilant by scouting their fields for Dickeya symptoms on a regular basis and by submitting any suspect samples for diagnostic testing. Dickeya dianthicola has been detected in the US in the past, and because of this, APHIS just recently announced that the pathogen has been designated as a non-reportable/non-actionable pathogen despite its potential to cause 100% crop loss. A link to the USDA/APHIS website for information on Dickeya dianthicola detection and control can be found here.
Unfortunately, there is a lot of misrepresentation of Dickeya dianthicola being presented to potato growers in the region.
- Dickeya is not a significant problem. To date its has been detected in seed in 12 states originating from 2 sources and a number of suppliers. In Maine, when dormant tuber testing was done for lots from 2015, there was approximately 16% incidence of Dickeya in 347 samples tested. In the dormant tuber testing for 2016, 25% tested positive for Dickeya out of 350 samples. Importantly, there is no current policy in place designed specifically for regulating and/or controlling Dickeya dianthicola in potato in Maine. There is also no way of knowing which of the above said lots (varieties) tested positive for Dickeya.
- Dickeya is Blackleg. Dickeya is Dickeya, not Blackleg. Dickeya is seed-borne. Blackleg is mostly soil-borne. Blackleg is caused by other ‘pecto’ or soft rot bacteria. Blackleg can be found in almost any potato field that has been in potato production in the past. Dickeya has only be found in fields planted with infested seed over the past few years.
- Dickeya is endemic. If so, why wasn’t it reported as causing significant problems in potato prior to 2015/2016. Even without proper testing available, it would have would been noticed by potato growers to cause concern/raise alarms.
- Dickeya is the result of the current environment. What has changed between now and prior to its first detection in the US in 2014?
- The disease is less severe 2016 than in 2015. Dickeya is being tested for and reported more often in 2016 now that it has been brought to the attention of potato growers. Growers who received infested seed are reporting variable losses to Dickeya in 2016. Growers who have planted back into infested fields are also reporting poor plant vigor and variable yield losses.
- Varieties differ in susceptibility to Dickeya. Dickeya has been detected in different lots of the same variety from different suppliers in 2016. Dickeya has also been confirmed in different varieties from the same supplier in 2016. Symptoms of Dickeya may appear different between cultivars.
The best method for keeping your potato operation Dickeya-free is to adopt your own 0% Dickeya-tolerance policy.
For more information on Dickeya please see the following articles posted online – source(s) of information:
Dickeya: A new potato disease – Growing Produce
Blackleg is Once Again Being Observed in Potato Fields Across the Mid-Atlantic Region – Penn State University
Update on Dickeya detections in potato – University of Delaware
Dickeya Blackleg: New potato disease causing major impact. – Cornell University
Watch for Dickeya – a new potato disease – The Ohio State University
High security Aroostook farm advances tater technology. – Maine Potato Board
Slowing Dickeya, other pathogens in Canada. – North Dakota State University
Dickeya: A new threat to potato production in North America. – SPUDsmart
Dickeya is coming. – University of Wisconsin/North Dakota State University
Maine ‘Ground Zero’ for new potato disease. – Maine Department of Ag.
Maine seed potato growers looking to protect brand against disease. Maine Department of Ag./Maine Potato Board
