scab on pototoes

Last year my spuds were riddled with wire worm and had a bit of scab on them.  theis year no wire worm but they are so scabby they look inedible without peeling about half the spud away, don't taste that good either.  the earlies were gorgeous and not scabbed much but the maincrop are awful.  can anyone tell me what causes this on spuds and what can I do to prevent it happening?  don't want to waste the entire crop but they're not going to store well and I grew enough to eat through the winter.

Scab is worse in limy soils. It is also worse if the crop is dry just after the small tubers have formed. Plenty of manure will help to retain moisture and make the soil more acid.

Many soils get overlimed. This does not matter too much on clay soil but on light soil it certainly gives more scab.

Some varieties are more resistant than others. See potato council website http://varieties.potato.org.uk/menu.php

It is common scab and not powdery scab that you are interested in.

I think the variety you grow is important. Last year I grew two first earlies in the same bed alongside each other. One was excellent (Arran Pilot) the other was full of wireworm and didn't grow well (Maris Bard). I'm sure that local people to your area will know what grows well locally and what doesn't and this might help get round the scab problem. Certianly some varities are much more resistant to scab than others.