Symptoms of gangrene include:
Discoloured, dark sunken and irregularly shaped areas on the potato. Gangrene also causes internal rot and cavities with sparse grey or yellow mould. There is no relation between internal rots and the size of the diseased surface area of thhe tuber, and it is common to find tubers with seemingly mild surface damange having severe internal damange. There is a clear and distinct margin between healthy and affected tissue.
The Phoma foveata fungus may be both tuber or soil borne. Plant ttems may become infected before in turn infecting the tubers. Tubers become infected with gangrene mainly through their skin being damaged during lifting, grading and in transit. The rot effects of gangrene are often not apparent until December or January.
Potato Varieties which tend to be more susceptible to gangrene include Shepody and Ulster Sceptre.
Cultural and Methods:
Gangrene cannot be treated, only prevented by planting only uninfected seed potatoes bought from a reputable source.
Ensure that the tubers are not damanged when checking the crop or harvesting. Harvest your potatoes soon after defoliation, especially during cold periods. If at all possible, cure your potatoes at 16-20°C (60-68°F) for between 1 to 2 weeks after being harvested, as this aids in the healing of tubers
Chemicals and Pesticides:
There are no effective chemical treatments available to cure gangrene in the UK, affected tubers should be destroyed immediately.