Nightmare plum tree

Not sure about the other tree problem but the yellow plums ripen very quickly. When you see them just start to yellow, check them immediately as they could be ready.
As for the withering part, plums are very susceptible to many plant diseases like peach-leaf curl, black knot, fire blight and others. Older trees were not bred to resist the problems, just for flavour. You just might have to pull the lot up and start with fresh, disease resistant varieties which won't sucker all over the place like the old varieties did.

The chainsaw might be the answer. My mother just took all her old ones down. They produced only every 2nd year....if they decided to produce at all, and they were full of diseases. I'd recommend that you also dig out the old roots which will only sprout again and create a fresh headache. Good luck.

The rotting fruit could be the work of the plum moth.  You can buy pheromone traps for these, but we did not find them very effective unless backed up by spraying the tree with insecticide one week after you have had a good catch in the trap.

Did you manage to taste the fruit? how large were they?  This could be a very delicious gage, which moths seem to prefer.

I have no idea what casued the withered bits.  I would cut them off.

Cheers,

Gillie

Can you see the graft?  I was wondering if this was a rootstock which had got away after the grafted plum had died, but if the fruit are almost Victoria size perhaps not. 

Winter is the best time for grubbing out so I think I would give this tree one more chance supported by some spraying - provided you do not need the land.

Otherwise - chainsaw.

Gillie

Oooops forgot to ask spray with what?

If you give the tree another chance, hang up bird feeders to attract the tit species who also enjoy the insects.
Also, rub grease around the lower tree trunk, even wrap a grease soaked rag around.  This prevents the male moths getting up to the females for mating.

I have my late Grandfather's cooker/eater apple (a Victoria type), which was moved from his previous orchard in 1937 and still doing well.  The apples are cookers when green, but sweet enough to eat raw once they've turned yellow (whilst still on the tree.) 

I also have his Worcester type apple tree which is at least 59 years old.  It was blown over in the 1987 hurricane, but one of my Sons helped my late Father plant it back in it's bed!!  We do have a few root stock shoots resulting from that time, but as the apples are tasty, I haven't cut that back.

My third apple tree is an Early Victoria, planted by my Father about 50 years ago.  We have had to cut out a lot of rotten branches, but still get lovely green/ then yellow apples......... similar to the fist one.

The latter two have such a heavy crop that we have to prop up the branches each year.