Rust or stress?

I need some advice. The spots on these apple leaves look like they could be caused by cedar apple rust, but 1) there are no cedar nor juniper within 600 meters, 2) we haven’t had the problem before, 3) there is little correlation between affected trees and those listed as being CAR susceptible, and 4) we are experiencing a moderate drought, and I associate CAR with wet, damp conditions.

I have regularly watered the young trees, but the older trees have not been irrigated. We were gone for week, so there was no watering, and our place received no measurable precipitation while we we gone. The amount of spotting of the leaves as well as leaf yellowing for trees with no leaf spots seemed much more prominent after we returned home.

I’m wondering if the leaf damage could be due to stress from the drought rather than rust.


The top and bottom pictures look like CAR and the middle one looks like black rot(?) CAR infection starts right after petal fall so the weather now is not so relevant. I haven’t found the CAR susceptibility lists to be more than a rough approximation. There is a chance it could be some other disease that happens to look exactly like CAR due to the weather conditions, but I would guess that the CAR blew in from further away due to the weather in the spring when the spores released. If that is the case it will hopefully be a fluke and will not be back. Or, you missed a juniper tree hidden somewhere. I don’t think your dry weather is a factor for the CAR at all, but other leaf diseases can be more prominent if the tree is under stress.


Thanks, Scott. That was my guess, but I had hopes of something else.