Diseased Apple tree

Asked June 8, 2019, 1:31 PM EDT

Last year, my apple tree manifested clear symptoms of fire blight. It was injected with an antibiotic and later in the winter, when it was still dormant, some of the branches were removed.
This spring it blossomed and leafed out nicely. But since then, the leaves are yellowing and falling off. Every day, a new batch of leaves fall, yellowed and showing other discoloration.
To me, this does not look like fire blight, but I am not an expert....
I've searched the internet and found things like Apple Scab, but I'm not sure if that's the right diagnosis.
Some photos are attached below. I would appreciate any help you can offer about how to save this tree. Thank you!

Denver County Colorado

1 Response

Apple scab is not usually a problem here because of our semi-arid conditions but, of course, we've had a lot of cool, wet weather this spring which might increase occurrence. Apple scab necrotic spots on the leaves are usually found along the mid-rib or in association with leaf veins with feathery margins; your spots seem to be more generally scattered across the entire surface and I can't see the margins. It may be that your yellowing leaves are more the product of hail damage (if you got it), too much moisture (or poor draining soils the effect of which is similar to overwatering), or some other fungal problem caused by weather which will abate as conditions dry out.

You could get an arborist out to take a look or you bring a sample in to either the Denver Extension office at 888 E. Iliff (720-913-5270) or the Jefferson County Extension Plant Diagnostic Clinic at the Jefferson County Fairgrounds. There is a small fee for the latter.

If by chance it turned out to be Apple Scab, the management would call for raking up and collecting fallen leaves and leaf debris which is a good idea to do anyway.