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Plant Health: weed, pest & disease management

Blackleg and soft rots

8 January 2018

Blackleg is one of the key diseases across all sectors of the potato industry in Great Britain. The disease is caused by a number of bacteria that have the ability to breakdown plant cell walls. They are referred to as pectolytic bacteria and include Pectobacterium and Dickeya species.

Pectobacterium atrosepticum is the major cause of blackleg in GB, although Pectobacterium carotovorum can also cause symptoms in the growing plant. Both bacteria cause tuber soft rot (decay in the field or during storage). These two species respond similarly under different environmental conditions and they are more common in cooler and wet conditions.

In addition, ‘Dickeya solani’ and Dickeya dianthicola can also cause stem rots, though they are associated with non-GB seed and are more damaging in warmer seasons. Control measures which reduce bacterial contamination on seed tubers also reduce the risk of soft rot and blackleg, although disease development is very dependent on the temperature and moisture levels in both field and store. 


Blackleg is consistently the main cause of downgradings and rejections in the Scottish Seed Potato Classification Scheme. In 2006 the incidence and percentage of crops failing to meet grade began to rise, peaking in 2011/12 at levels not seen for 20 years. Although environmental conditions undoubtedly play a part they do not entirely explain this rise and in any case climate predictions would suggest that conditions in 2011/12 may not be that unusual in future years. Blackleg is currently the focus of a Potato Council/Scottish Government funded R&D project exploring sources of infection and spread in early pre-basic generations. 

Research Project 114R75: Routes of Pectobacterium Contamination of High Grade Potato Seed

Dickeya spp. (Blackleg)

These pages aim to provide current information on the Blackleg pathogen for potato producers and industry in Britain.

Dickeya (formally known as Erwinia Chrysanthemi), is causing crop losses and increased costs to continental European potato growers. It produces Blackleg-like symptoms, but appears to be much more aggressive and active at higher temperatures than 'traditional' Blackleg produced by Pectobacterium.Unfortunately Dickeya is not a notifiable disease like Ring Rot or Brown Rot. However, testing has indicated that Dickeya isn't present in potatoes that originate from domestically produced seed.

Scottish Government leaflet on Dickeya Solani.
'A new threat to the potato - Dickeya Solani'

AHDB Potatoes Grower's Advice on Dickeya - Blackleg:
Dickeya - 'What it is and what you can do'

Disease advice - video interviews

View the seminar from Dr Gerry Sadler (SASA) on the threats Dickeya poses to British potato production, what it looks like, the current state of play and what can be done to protect your business against Dickeya.

The seminar has been split into two recordings - please watch Seminar: Part 1 first.

Sourcing seed produced in the Safe Haven Certification Scheme is a major tool in reducing the risk of Dickeya.


Dickeya Seminar: Part 1


Dickeya Seminar: Part 2


AHDB Potatoes R&D activities on Dickeya:
Investigation of Erwinia chrysanthemi (Dickeya dianthicola and other Dickeya spp.) able to infect GB potatoes (COMPLETED October 2008)

Link to Scottish Government advice on potato quarantine diseases.

For further information on Dickeya and how the Safe Haven certification scheme can protect your business, contact:

Robert Burns
Head of Seed & Export
AHDB Potatoes
tel: +44 (0)131 472 4064 |

2017 PIlot Study Resutls

Resutls from the Post-harvest testing of Scottish Pre-Basic crops for the management of potato blackleg disease can be found here