Aug 30, 2016
Dickeya remains concern in Pennsylvania

With the persistent warm temperatures and some much needed rains falling across Pennsylvania, it is important to continue scouting for blackleg-like symptoms. So far this season Dickeya dianthicola has been confirmed on potato in 11 states from seed lots originating out of Maine as well as New Brunswick, Canada. Those states are Delaware, Florida, Maryland, Massachusetts, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, Virginia and West Virginia.

Symptoms caused by Dickeya infection are very similar to those caused by Pectobacterium atrosepticum. It can manifest itself as poor seed emergence as well as a water soaking and blackening of the stem pith and vascular system under wet conditions. The leaves then become yellow and curl upward. It also can cause a soft rot of potato tubers since the bacteria are able to degrade or feed on the pectate found in the cell walls causing them to break open and leak their cell contents. The disease is favored by cool temperatures below 65°F and moist conditions.

Unlike Pectobacerium that can be soilborne, to our knowledge Dickeya dianthicola is primarily seedborne and once symptoms develop in the field, management tool are severely limited. The best management tool is making sure to purchase uninfected seedlots. This will be a challenge as there currently are not any standardized seed testing protocols for Dickeya in seedlots. This season it is important to identify problematic seed lots and work to eliminate them from the production system. If you suspect black leg in your field, please contact me by email or by phone at 814-865-7328 or the Penn State Plant Disease Clinic. We are interested in collecting samples to determine whether the symptoms are caused by Pectobacterium or Dickeya using molecular-based diagnostic approaches. We are also in the process of submitting for grant funding to better understand the biology, epidemiology and disease development to help minimize further losses.

For more information, visit the Penn State Extension website at

75 Applewood Dr. Ste. A
P.O. Box 128
Sparta, MI 49345


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