A fungal disease that attacks stone fruit trees, and fruit with cores by destroying the blossom, e.g. Cherries, Plums, Apples and Pears.
This is the same fungi responsible for causing brown rot in the same fruit types.
Brown rot infects through wounds caused by birds and wasps so, if possible, net to reduce bird damage, and if the net is fine enough this may also deter wasps.
The disease is climate dependent and the severity can vary due to this, i.e. the spores are spread in humid conditions by wind, rain and insects.
The condition causes the blossom and leaves on flowering / fruiting spurs to wilt and shrivel up.
Later in the season the fungus will cause the fruits to shrivel.
The fungus is seen as buff coloured pustules on the leaves particularly under damp weather conditions.
The fungus can over-winter in dead fruit and cankers on the trees, then it releases its spores in spring, to cause the same problem/s again.
Unfortunately, once the symptoms are present there is little that can be done.
Fungicides are no longer available to the amateur gardener, copper based fungicide or Bordeaux mixture may give some control.
The best way to prevent the fungus over-wintering in the bark of twigs is to prune them out,and remove any diseased or damaged fruit from the tree.
Also, remove any potentially diseased debris that has fallen from the tree, including any shrivelled fruits.
Do not store any affected fruit and do not pull any stalks from fruit you are intending to put into storage.