A potato disease which has not been found in Ireland before, potato brown rot, has been identified on a tillage farm in the southeast.
Brown rot is caused by the bacterium ralstonia solanacearum. and has the potential to cause significant yield losses through the rotting of tubers in affected host plants.
Although the disease poses no risk to human or animal health, the Department of Agriculture and Food has launched a major operation to prevent its spread to protect the national potato crop.
The disease was detected initially in water samples taken as part of the department's routine control programme at a potato-packing premises and traced back to a farmer supplier.
All potato stocks on the farm were sampled and to date there is one confirmed positive.
In addition, related potato samples from two potato-packing plants have been confirmed positive.
Holding notices have been issued to the grower and to the packers involved to prevent movement of potentially infected stocks.
All stocks have been isolated under department supervision pending the taking of the appropriate disposal action.
The normal source of infection for brown rot is infected seed or through infected water.
As part of the further investigation, extensive sampling and testing by the department of possible linked sources of infection are ongoing.
The first visible symptom of the disease in potato crops is wilting of the leaves at the ends of the branches during hot days with recovery at night.
A streaky brown discoloration of the stem an inch or more above the soil line may be observed as the disease develops and the leaves have a bronze tint.
Disease development occurs at different rates in different varieties, but is favoured by warm temperatures (above 15 degrees with an optimum of 27 degrees) and high soil moisture levels.
External symptoms may or may not be visible on tubers, depending on the state of development of the disease.
Worldwide, ralstonia solanacearum has an extremely wide host range.
However, the bacterium which affects potatoes has a limited host range, but includes tomatoes (lycopersicon spp.) and the weeds solanum dulcamara (bittersweet) and solanum nigrum (black nightshade).