Pectobacterium atrosepticum (previously known as Erwinia carotovora subsp. atroseptica) is the cause of potato blackleg in Scotland. Although blackleg and the associated soft-rot of tubers in store can cause severe economic losses, it's occurrence and severity are dependant on environmental factors in the field (temperature, rainfall, poor drainage etc.), timing of harvest and seed storage conditions.
Blackleg affects the lower part of the stem, producing a brown/black rot accompanied by a distinctive smell, often accompanied by yellowing/curling of the leaves. In early and severe cases, plants may not emerge or are stunted, yellow and die quickly post-emergence. The disease is spread by infected seed tubers, which when planted can infect daughter tubers through the vascular system and can infect neighbouring plants through groundwater as infected tuber begin to decay. Decaying tubers can also infect healthy tubers at harvest or in store by direct and indirect contact.