Hello all. This is a Santa Rosa plum tree that I thought had a bug problem but as I noticed the leaves and looked a little closer it appears to be rust? I believe the treatment for it because it is a fungus would be to apply a copper or sulfur before the season begins right? But is there anything that I can do to it currently? Should I try and apply a different type of fungicide? Or should I pick off the leaves that are infected? I know definitely to clean them up after they have fallen and get rid of them so I will be doing that for sure. But what are your suggestions?
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I checked Penn State, I think your leaves looked more like bacterial leave spot.
See the link.Plum and prune | Diseases and Pests, Description, Uses, Propagation.
Wow I didn’t even think about that. That is a great website as well. Thank you. This is the underside of the leaves and a better shot of the top.
Penn State extension service is a great resource. So is Cornell for the east coast.
I don’t see shot hole in plums as much asin peaches. If you have several peach and plum trees, look into Kocide 3000, copper hydroxide. It’s worth your money for fungicide and bacterialcide all in one.
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Cool. So should I treat now and throughout the summer? Or is this a type of disease that if not treated early spring it just has to run its course?
Right, it is treated in spring and fall with copper sprays for example. There is not much to do now.
I had had a lot of problems with shot-hole on some asian plum varieties. Santa Rosa is not as bad as some other varieties, Howard Miracle for example was just horrible.
That’s crummy to hear. Thanks for the info! All of you.
Hey Scott. I’m going to go out this next week and put down a dormant oil spray. I had a problem with the bacterial leaf spot on my plum tree last year and your recommendation was some copper spray. My plan was to spray them with monterey dormant oil spray or some bonide neem oil That I had left over. What one would you suggest that would be the best dormant oil spray? Would either of these fix my bacterial leaf spot issue? and if not I was going to buy this montereys liquid copper to mix with the horticultural oil. What do you think?
Also I’m just curious if maybe I should just leave it alone. It was the first year and it was only on one tree. If I were to not treat it with copper would it come back? Or would there be a chance that I would have no issue this year? I would still do a dormant oil spray but just without coper
Hi Chris, you need copper for bacterial spot, the other two things will not help at all. New plants often get it as they are weaker and it might grow out of it next year. Or, maybe it was bad enough and it could end up spreading more. I had some bad outbreaks and if it was me I would lay down copper this spring to be on the safe side. That Liqui-Cop I have not used, it says 8% copper so make sure you use enough of it.
Ok great. Do you feel it is OK to mix with the horticultural oil?
Yes, for dormant sprays you can mix anything together.
Ok awesome! Thank you. 
I am sorry last question. Should I spray all peach, plum an apple trees or just the trees that were affected last year? I think my peach tree got a little bit of it but just the one plum tree was the main affected one.
And I assume I am spraying trunk and branches all the way to tip?
I wouldn’t bother spraying the apples but would hit all stone fruits. Mainly you need to hit where leaves will appear.
On my bottle it has 27% Copper listed.bb
Ok thanks Scott.
Thanks Brady. That is actually what I was going to look up.
Hi again Scott. I finally got out and sprayed my trees today. I mixed a full gallon thinking it would take that much but it only took a half gallon. I mixed copper with horticultural oil. Is it possible to save the other half gallon and spray on again in a few weeks Or even fall? Is that recommended or is only one spray enough? I could also go over my trees again a second time tonight or tomorrow if you feel it would help. If not I will just have to find a way to dispose of the spray. I looked at your other postings and didn’t quite see answers to these questions.
If oplea is able to answer that would be OK as well. I just don’t know how to add him to this thread if needed.
When I have extra I usually turn around and give another coat, it never hurts. I have thrown away spray before but really do not like to do that.
Ok cool. Thanks