Plant Health

Risk assessment of Ralstonia solanacearum – brown rot on potatoes from the Netherlands


Report no: 2010: 39

Published: 06.12.2010

Main message:

There is a medium probability that the bacterium Ralstonia solanacearum that causes the plant disease brown rot in potato is introduced to Norway via potatoes imported from the Netherlands. That is the conclusion in a risk assessment the Norwegian Scientific Committee on Food Safety (VKM) has done for the Norwegian Food Safety Authority.


The background for the request is that Dutch plant health authorities have asked the Norwegian Food Safety Authority to reconsider the current import ban on potatoes from the Netherlands.

They refer to the decrease of brown rot in the potato production, as a result of the control measures that have been implemented during the last few years.

The Food Safety Authority has therefore asked VKM to assess the probability of the bacterium Ralstonia solanacearum being introduced to Norway if the current import ban is terminated and import of potatoes for food or industrial purposes from the Netherlands is allowed. The Food Safety Authority has also asked VKM to assess the consequences if R. solanacearum establishes in Norway.

The pest brown rot in potatoes is caused by the bacterium R. solanacearum. The bacterium can also attack wild plants, such as bittersweet and black nightshade. Brown rot has never been observed in Norway.


The probability of introduction of Ralstonia solanacearum to Norway by the pathway for entry of ware potatoes for food and industry purposes grown in the Netherlands is expected to occur at a rate of entry in the range from 1 to 6 per 100 000 lots imported.

Converted to numbers corresponding to the current potato import, the frequency of entry of brown rot to Norway will be an average of one infested potato lot being imported between every 10 to every 60 years.

One single incident and further spreading of the pest from the entry site will, according to model simulations, in average affect 90 hectares potato field, at worst up to 900 hectares depending on where in the country the pest is introduced.

The VKM panel on plant health was responsible for the risk assessment.


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