The time to do this is anytime between leaf fall & bud burst, autumn / winter. Take out any dead or diseased wood first, then any branches that are crossing, then any branches that you just don,t want. You may lose some fruit in the first year, but will be better in subsequent years. derekm

Don't attempt to prune your plum tree until April, only whilst it is in leaf or you will introduce silver leaf into the tree.

Yes, I agree with that , but it can be prevented by using fungicidal paint on the cuts, and feeding. derekm