Question
Dear James ,we have had extremely wet weather on lifting my early and second early potatoes they are covered in white nodules approx 1 mm in dia they rub off easily . does not seem to affect the skin thank you

Answer
Hi Ron, from your description, I'd say it's not fungal, just a physiological condition related to excessive moisture and possibly excessive fertilizer.  If, after storing a while, sunken lesions form where the spots were removed...then I'll change my mind. Let me know if they start to go bad and we'll address a preventative program for next season.  Jim