[steampig]

Just dug my pink fir crop, only to find this:



Checked out this useful site:

LINK

Not sure if it's scab. This is my third year of growing pink fir, previous harvests have been fine. Also an adjacent bed of desiree wasn't affected.

Please help, is this a serious problem ?

[WG.]

Looks like common scab from having free lime in the soil

[steampig]

Sorry WG does that mean I need to add lime or not, I tested the soil last summer as neutral

[WG.]

The problem is caused by having free lime in the soil.  DO NOT lime before potatoes.

[steampig]

TBH I havn't used lime at all in the four years iv'e had my lotty, never sure how to, how much to, or when to :oops:

[shaun]

have you got lime stone paths/road adjacent to your plot ?

[steampig]

No, we're surrounded by pasture, but the local farmer has been known broadcast what I guess is a chemical fertiliser over his pasture and I got a free covering  :twisted:

[shaun]

the scab ive seen looks nowt like that picture,the scab that we get is more of a realy rough skin on the spud :?

[muntjac]

you need to dig in loads of manure /compost .and lime 1 oz to  square yard the bit this year for over winter brassicas and when they have finished you can plant the spuds in that ground , i dont think its scab as you have peduncles sprouting on the spuds where as with scab they look round in formation and  are like dried skin with a rosette defoliation. i  cant say what it is  i think it needs further investigation at the rhs .parcel 2 specimens up in dry cottonwool and send them to the rhs with your name and address  ask for a diagnosis and treatment if there is any ., the
royal horticultural society can be found on the net for addresses

[steampig]

That's what I thought I have had slight infections of scab before. This time it's more like blisters, on some spuds the blisters have "joined together" into larger areas. Also the yield is very low compared to other years.

[WG.]

This time it's more like blisters, on some spuds the blisters have "joined together" into larger areas.

Mmmmm, not sure any more.

I had a look at the link you originally posted, and it says, describing common scab, "Symptoms : Range from slightly corky lenticels to extensive raised or pitted scabs".

What type of soil have you got, heavy or light?  If you do send off to the RHS, please post to let us all know.

[steampig]

Medium I'd say, but I'm no expert, underlying bedrock of sandstone, also I grew these in raised beds so the soil was pretty free draining.

[steampig]

Will try to post some away by the weekend, I just wanted to make sure it wasn't anything obvious.

 Watch this space