Pruning some old damson plum trees

Julia pruning a 25 year old damson plum tree (variety Merryweather). Plums should only be pruned during a period of strong new growth, for us that means mid April to early May. This is because of the risk of microbial disease entering pruning wounds. We don;t think wound paint makes much if any difference. We have lost most of our plum trees from boring insects and bacterial plum canker, we won;t be replacing them, which is a pity as they can be lovely trees. One variety, Blue Tit, seems to have resistance and we hope to report on this in the future.