someone wrote:
"David in Normandy" wrote in message
. fr...
Any ideas what cause this? I'm just curious. It doesn't seem to be
directly related to slug damage as the black / grey mass can
sometimes be quite deep inside otherwise apparently pest free
potatoes.

Could it be internal rust spot?

http://www.potato.org.uk/department/...f.html?item=42

If not that, then maybe blight or gangrene.

It doesn't look like those when I see it. My money's still probably on
bruising: see at
http://www.potato.org.uk/department/knowledge_transfer/pests_and_diseases/ref.html?item=33

--
Mike.