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Blackleg stem rot and tuber rot caused by Pectobacterium    

Symptoms in the following photographs were seen on a high percentage of tubers of variety Vivaldi at harvest on 21 September 2017.  Rot was at the stem end.  Pectobacterium parmentieri (formerly P. wasabiae) was detected in affected tubers.  An intense rain event on 18 August 2017 might have helped move bacteria from stems to tubers.  The weather station at LIHREC recorded 2.86 inches of rainfall over 2 hours, with most during 1 hour (http://newa.cornell.edu/index.php?page=weather-station-page&WeatherStation=riv).

pectobacterium

pectobacterium

pectobacterium

Following photograph of planting with aerial stem rot was taken by Sandra Menasha.

pectobacterium

Pectobacterium spp. are managed primarily by planting uncontaminated seed in a field where potatoes were not grown the previous year.  Aerial stem rot can be managed with applications of copper fungicides.

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