Hi John,
Apple trees are usually pruned in winter. If you prune now, you will be
pruning out flowering buds (this year's fruit). Sorry, don't know about
pears. Never prune your plum or cherry in winter (due to risk of Silver
Leaf fungal attack). Prune these in summer during good, dry weather.
The black spots on your apples are probably Apple Scab. It's a weakening
fungal disease which needs to be treated. Ask at your local garden centre
for an appropriate fungal spray or its organic equivalent. You will need to
clean up the whole tree, otherwise any fungal spores you miss will re-infect
the tree.
It also sounds as if you need to feed these old trees, and ensure they get
enough water during the growing season. Are they surrounded by turf or
weeds, which will compete for nutrients and water? If they are, it would
certainly help to clear a wide area around them. When they start producing
flower buds, gently fork in some fertiliser, water well and give each tree a
thick mulch to hold that moisture in.

Since you're interested in fruit growing, I think a good book on the subject
would help.
Spider


John Horne wrote in message
...
I have inherited a gang of fairly old apple trees, and I have also planted
some
plum, cherry, and pear trees. The meagre fruit produced over the last two
seasons have had lots of black spots on them, mainly I have to say in the
old
trees. I feel I should spray them with something, or prune them or
whatever.

So should I prune and if so when? Should I spray with something and if so
when
and what with?

John (a total novice, who is keen to learn..!!)