Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu and Andy Wyenandt, Specialist in Vegetable Pathology, Rutgers University; wyenandt@aesop.rutgers.edu
The potato season in winding down and growers should be thinking about what they will do next season as far as sourcing potatoes. Unfortunately, there is a lot of misrepresentation of Dickeya dianthicola being presented to potato growers in the region. Some examples are as follows:
- Dickeya is not a significant problem.
The truth is, to date this pathogen has been detected in potato seed in 11 states, originating from 2 sources, from numerous suppliers. There is no current policy in place designed specifically for regulating and/or controlling Dickeya dianthicola in potato seed, although such policy has been presented in the past.
- Dickeya is Blackleg.
This is like saying Jay Cutler and Tom Brady are the same because they are both quarterbacks. Dickeya is Dickeya, not Blackleg. Dickeya is seed-borne, Blackleg is mostly soil-borne. Blackleg is caused by other ‘pecto’ or soft rot bacteria. Dickeya causes disease at much lower levels (fewer bacteria needed to cause disease) than blackleg. Typical disinfestation works for blackleg, but do not work for Dickeya.
- Dickeya is endemic and caused by the current environment.
Dickeya dianthicola only has been reported as causing significant problems in potato since 2015. What sudden environmental shift has caused such a widespread outbreak of this disease over this time over such a wide, environmentally diverse region? Even without proper testing available, it would have would been noticed enough by potato growers to cause concern/raise alarms and likely would have been observed much more frequently if it had been established at significant levels for several decades.
- 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.
- 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.
The best method for keeping your potato operation Dickeya-free is to adopt your own 0% Dickeya-tolerance policy.