what disease does my potato have (picture)?

[Snadger]

Individual plants can be affected by blight and the rest can be ok. Also tatties that appear to be alright when you dig them can develop internal rot at a later date!

[King Carrot]

I've been growing my spuds in the same spot for 3 years now - it's really only good for spuds as the surrounding tall trees cover it over by early summer with their leaf canopy so I try to get them in by March or as early as possible . By trying various varieties and spacing the rows 4ft apart I've just had my best crop ever in that plot. Charlotte, Kestrel and Orla have all had good yields although the Orla were progressively full of more and more slug holes. Sarpo Mira and Setanta still to come.

Sometime before planting (sometimes just before) I dig a trench a foot down, sprinkle a complete fertilizer which I then dig in to that trench loosening a further 6 - 10 inches then I fill in the trench adding seaweed and any horse or cow manure I can get hold of, I then put the seed potato at the required depth (usually not too deep to get quick growth and a big plant before the light goes due to the tree canopy)

I'd rather rotate and recommend other people to rotate, as I do with everything else but nothing else will grow in this bit over the summer anyway so I’ve nothing to lose really by carrying on with the spuds there.