I'm Seeing Spots

Cedar apple rust on an apple tree

One of our new apple trees has cedar-apple rust.  I first noticed these spots in late May and did some reading.  I found this excellent fact sheet from the University of Arkansas.

Here's a quick rundown:

Cedar-apple rust is a fungal disease with a lifecycle requiring both cedar trees and apple trees (or crab apple).  It forms very interesting looking baseball sized orange galls on cedar trees, but doesn't really hurt them.  The problem arises in late spring, when it infects apple trees with the leaf spots seen in the picture above.  It causes early leaf drop and can also infect the apples themselves.

So what do you do about it?  The best answer appears to be to only plant cedar-apple rust resistant varieties.  The fact sheet I linked to above has a list of resistant varieties.  Our Pixie Crunch tree is not on that list.  We could treat the tree with a heavy duty fungicide like Daconil, but it would just get infected again and I don't like to use chemical fungicides anyway.  We will treat this tree with Serenade, an organic treatment containing a microorganism that eats fungi.  If the tree doesn't respond, we may have to just get rid of it and be more aware of this disease when we select our new varieties.