Newbie - White Spots on Potatoes
 

Hi all

I am harvesting my first ever potato crop - Pentland Javelin earlies.
They have small white spots on the skin which rub off OK for cooking.
What are these?
I have only recently started harvesting these.
Will the potatoes left in the ground for longer periods suffer further ill
effects from this?
How do I prevent this returning next year?

TIA

Phil