Symptoms of Dickeya blackleg in the photographs below were found the first week of June 2016 (starting May 31). Affected plants had black stems extending up from the plant base and rotting seed piece, typically with an earthy smell that occasionally was offensive indicating soft rot bacteria were also present. High temperatures (in the 80s) during late May provided conditions favorable for symptom development. This pathogen is difficult to manage when developing in a crop because it is inside stems moving upward. In contrast, Pectobacterium, the pathogen causing the type of blackleg occurring in the past, starts on the outside of stem tissue, infects through wounds, and then moves downward as well as upward causing stem rot that is dark brown. Affected tissue typically has an offensive odor. Certified potato seed that is free of Dickeya is key management practice for this disease.
More information on the Vegetable MD Online website.
The following photographs were taken in commercial potato crops on Long Island by Sandra Menasha, Vegetable/Potato Specialist with Cornell Cooperative Extension-Suffolk County.
