[gypsy]

I have a bag of potatoes growing in my green house and over the last 2 days they have developed tiny white spots on the upper surface of some of the leaves. Does anyone know what it is and if I should be doing anyathing about it please.

[Kleftiwallah]

How tiny is tiny and have you inspected the lower surface?

Cheers,    Tony.

[GrannieAnnie]

Sunburn?  Water burn?

[JayG]

Was going to mention sun scorch too, but thought it might cause a hollow laugh! 

If it's just the older leaves it's still the most likely possibility, as they will be getting a bit tired now and will have no doubt been wetted and seen at least some sun since they first appeared.

[gypsy]

Thanks for your interest folks, the spots are about as big as a pin head, raised on the upper surface of the leaf and just visible on the under surface. They do not completey cover the surface of the leaf, parts of the leaf look healthy, some of the leaves have minimal frost damage from about 2 weeks ago when I did not cover them as I thought the greenhouse would have been adequate protection but was wrong. Sorry can not do photos. I wondered if it was some sort of virus or maybe over watered a bit. CC