Q How do I know if my potato plants have blackleg?

A The potato-plant leaves are small and yellowed, and may be distorted. The stem base shows distinct blackening and then dies back. The vascular stands are blackened so cutting the stem across reveals black 'dots'. The 'mother tuber' rots completely and if the bacterium Erwinia caratovora var. atroseptica strikes early, the plant may be killed and will not crop. Wet soils tend to exacerbate the problem, which is usually introduced on a symptomless seed potato, often via wounds.

Caption: Blackleg causes the base of the stem to turn black and die back

Q What should I do if my potato plants have blackleg?

A Remove affected plants as soon as you see them. Lift crops in dry weather and only store potato tubers that appear to be in perfect health.

Q How can I prevent blackleg on potatoes?

A Buy seed potatoes rather than saving your own. Grow them in a new site every year to avoid 'volunteer' potatoes which may be infected. Improve drainage if your soil is wet. Choose resistant varieties such as 'Charlotte' and 'Vales Sovereign'.