This is occurring on multiple cherry varieties in the orchard, all on Maxma 14. The leaf depicted is on a Stella.
The closest explanation I could find is Cherry Leaf Spot, but it does not look the same. This starts on the outside and the discolored area is for the most part continuous and not individual spots. Besides, I can’t see any purple coloration on the underside…unless I’m colorblind.
And what could be done to prevent this from spreading if this is in fact a disease?
EDIT: I just now saw the Insect and Disease Identification Thread and should have posted it in there, but I can’t unfortunately delete this post. My appologies.
You can start your thread here you don’t need to put it in the Insect and disease identification thread. I actually prefer that separate threads are started because it makes it easier to find specific problems for people answering questions and those using the search function of the forums.
It could be cherry leaf spot. I think it probably is not. The problem is we are late in the year and leaves tend to get beat up when they are this old. The individual spots tend to merge and become masses. So many diseases are less distinctive and harder to identify. It’s usually easier to identify diseases earlier in the season.
I get a fair amount of cherry leaf spot. It’s much more of problem on tart cherries. I find the purple coloration is often not distinctive… you get more of a brown with purple tint depending on when you’re looking at the leaf, it’s condition,etc. Usually the spots are smaller and have more distinct borders than in your pic. They are usually more numerous too. Here is a link with pics. Cherry Leaf Spot and Fire blight? - #2 by mroot
But I am in a different climate (Illinois zone 6) so maybe it looks a bit different in California- perhaps @Stan or @Vohd could comment on what they think the cause is.
Let’s just say for the argument that it is indeed Cherry Leaf Spot. We’re about 1.5 months away from leaf drop. Should I do something about it or let it run its course? Should I do something during dormancy?
At this point I wouldn’t spray anything since it won’t do much good. Most fungicides protect the leaves. They can’t cure an infection. You can get rid of the dead leaves when they drop to remove the spores. Usually spraying starts in the spring and Daconil, Captan, Immunox are fungicides you could use. You would want to review the label before buying any of these.
