Can't help with the plum tree problem but would suggest you edit your question and remove your email address. Any GoY member replying to you will do so in the same way I have and you are leaving yourself open to being spammed.

Hi Jackierees - I too have a 5 year old Victoria Plum tree and the same thing happened to mind last year. I investigated at my local garden centre and was advised that probably there were a few 'plums' left on the tree from the previous year that had not fallen, had then dried on the tree and became infected from insects. When the new blossom came last spring the insects infected the blossom and subsequently the new fruit which was forming, therefore all the fruit was infected at the earliest possible stage. I lost every single piece of fruit. In the previous years I had heavy and good crops. I was advised to ensure every single plum and leaf that had not fallen from the tree by the beginning of autumn was removed manually and burnt. I was then advised to 'wash the tree' with a solution of soapy water (I used a pressure washer to do this) and then to tie a special band around the trunk of the tree - beneath the lowest branch - this is an insecticide which would stop a new infestation
I carried out this procedure 'to the letter' and am now waiting to see if it has any effect on this year's crop. I will update this as and when - Good luck with yours, mary 1229