After harvest you should be looking through your bags of stored potatoes to see if they are still healthy. You should remove any rotted tubers so that the rot does not spread to the healthy ones. You might find tubers with sunken areas on the tuber surface but the tuber is still firm.
When you split open this tuber you might find that the rot is chestnut brown in colour and is spreading in to the centre of the tuber. This is what happens when the blight spores on the leaves and stems are washed off the foliage into the soil where they can infect the developing potatoes.
Infected tubers like this might survive and if planted for seed and can produce an infected stem soon after emergence. That is where early blight infections come from, sometimes as early as April.
Also if you dump the rotted potatoes into a convenient ditch or rubbish tip, infected sprouts can develop. The motto is ‘bin or burn’.
Sometimes the blight allows soft rot bacteria to penetrate the potato to give a smelly, dissolving mass. Not a pretty sight.
Fortunately this year most growers did not experience late blight and so tuber infection was quite rare.
Our Sarpo varieties all have high resistance to tubers blight. So even if blight is present in your plot you will be unlikely to have any tuber blight on your Sarpos. Even some modern varieties have little resistance to tuber blight and there are many varieties with little or no foliage blight resistance that have good tuber blight resistance eg the second early, Charlotte. Check up on the blight resistance of any variety here.