Gangrene
Phoma exigua var. foveta
Pathogen
Fungus
Hosts
Potatoes
Symptoms
Small dark `thumb print` depressions in the tuber skin. The rot inside the tuber is usually surrounded by a black / brown margin.
Development
The disease originates from inoculum on seed tubers, which subsequently infects the surrounding soil. Daughter tubers are infected through wounds caused during lifting. Rotting develops during storage at the wound sites and usually becomes apparent in December or January.
Favourable Factors
Dry, cold lifting conditions followed by cool storage. Tubers become more susceptible as they age.
Importance
Can result in serious storage losses.
Control
There are no known resistant varieties, but information on less susceptible varieties is available on the National List
Plant disease free tubers
Minimise mechanical damage during harvest
Hold freshly harvested tubers in warm, dry conditions (13 - 16C) for 10 days to encourage rapid wound healing
Treating with fungicides and or fumigants may reduce disease incidence during storage
