Hi Alan- Your great pictures show me a tree that has been stressed by the weather this year and has developed a fungus infection along with aphids. The leaf spot fungus is causing the holes and the "white spots" are the cast off carcasses of the aphids.

For the aphids, at this time of year a strong jet of water from a hose is recommended to knock back the population. There should be helpful insects like ladybugs and lacewings helping you out as well, so you don't want to spray chemicals now as it would harm the good and the bad guys.

The fungus is also called "shothole" and I'm attaching an article for ways to deal with it. It is common this year due to our wet spring. You can prune the tree for more air circulation and rake up the fallen leaves to keep it from entering the soil. There are some sprays in the following article that can be applied to the tree this fall at "leaf fall". Look for the ones listed that have an "H" with a box around it. These are available to the home gardener.
https://pnwhandbooks.org/plantdisease/host-disease/prune-plum-prunus-spp-leaf-spots

I did not get good pollination on my Italian plum this year due to the rain, so don't worry if you don't have much fruit. It is not related to the aphids and shothole.

Happy spraying,

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