Never seen this before on potato leaves and I have been growing them for over 40 years. Anyone any ideas? Not insect eggs and eventually the leave curl up and rot.
Looking through Mr Hessayon's book, it looks like 'Mosaic Virus' - treatment: none. Prevention: use virus free seed. Spray with heptenophos to control the virus carrying aphids.
Further reading of Alan Romans potato book also seems to point to the same conclusion, plants may produce a very poor crop.
Hope that helps.
Not so sure about it, these were Certified seed potatoes from a reputable Scottish grower, so they ought to have been free of Virus. The images I have in my Pests book do not look like these green pustules on the top leaf surface.
Not something I've ever seen before either
If it is a virus then I would get rid of all the infected plants asap, heart breaking I know but these can be spread quite quickly.
Is it isolated to one or two plants or your entire crop?
It is on the all the ones we planted in the polytunnel, but the ones outside, same variety, Sharpe's Express, are not through yet.
They will be disposed of!