Thank you for all your replies, I will try to give a little more history.
1: The horse manure was a shared load between ourselves and another plot holder across the way from us, he has not had any of these problems, in fact his crops are looking wonderful. His potatoes are going great guns.
2: The plotholder ajoining us had a load delivered early this year from the same place and he has no problems either.
3: We work on a 4 year rotation, all the other spuds are doing fine, the haulms are looking very green and healthy.
4: The manure was also used on our brassicas/leeks/onions and lettuces with no problems.
5: We have 2 seperate A-frames of runner beans, the one A-frame is perfect, but the leaves are looking a little pale. The other A-frame is on the same side as the potatoes, lthese are also looking very pale and one side of the beans have withered and died, so had to resow more r/beans to replace them.
We don't use any weedkiller or sprays on our lottie or at home so that rules out any grass cuttings
After reading Iain@JBA's post I think he is right "chemical poisoning"
Why do I think this, well I am chairperson of our allotments committee and about 3-4 weeks ago there was a malicious attack of vandalism on our plot by another plotholder, whom I must have offended doing my duty. No other lotties or crops where touched other than ours.
We have built 2, 12'x10' brassica cages, one night somebody slashed the complete side of one of them and pushed down one of the runner bean A-frames. The rest of the plot and crops appeared to be ok, this would be about a week before the potatoes showed these symptoms.
My lottie neighbour had thought it was deliberate poisoning but we did not think that there would be anyone that would stoop that low, still you live and learn don't you.
Opinions please.
vron