Not sure,..it could be Shot Hole Disease, a bacterial pathogen.

I agree it looks like shot-hole, aka bacterial spot. Treat with dormant copper at leaf fall and again right before bud break in the spring. Google the term to read up on the disease.

Scott

Thanks for your insights guys. After reading up on shot hole disease I think that's what it is. But I don't like the idea of sitting around for a few months and only taking action in the fall.

A few things:

1- Is there anything I can do now to kill the disease?

2- If not, is there anything I can do now to prevent the further spread of the disease throughout my tree?

3- What can I do to prevent the spread of the disease to my neighbouring fruit trees/plants (i.e. asian pear, european pear, other chum tree, raspberries, strawberries, grapes)?

4- Should I remove and burn all damaged foliage? Prune the tree?

Thanks again
Jon

Here is a link that might be useful: Cherry Plum Tree Foliage Problem

If there are enough non-damaged leaves it helps to remove the damaged ones. I have heard various proposals for other sprays to use in growing season but have not seen a convincing enough case for any of them.

Scott

Oh I forgot about your question 3. Your other chum tree is susceptible but none of the others - only stone fruits.

Scott

I think a healthy tree can overcome this problem,...had it on a plum tree once, so then I wanted to make a drastic change in diet/nutrient in the soil to see if it might work, not knowing what was lacking, this tree had also funny whitish leaves like mildew, I then dumped about a 100lb of cast iron shavings from the machine shop around, the tree has been good since.

Konrad is right, healthy trees can fight back and don't get spot as badly. I didn't notice the tree was a recent transplant, that means it is highly susceptible since it lacks good vigor. I would not worry so much, once the tree gets going it will be much more resistant to the disease.

Scott