Navel Orange Blight
Attached are pictures of a problem that I have started having with the navel oranges from the tree in my backyard. I have a single navel orange tree that was already in the yard when we moved in in 1971 and this is the first time we’ve had any problems. The problem is occurring on almost all of the ripe fruit. It starts on the on the navel side, but it is not always readily visible from the outside. I'd like to know if you can help identify this problem and suggest a course of action. I’ve been to several local nurseries, but they have been unable to determine the cause. I'm concerned this condition could spread to the other citrus trees that we have in the yard. I can arrange to send additional samples if you'd like. Thank you for your consideration.
Damage navel orange - Advanced stage
Damage navel orange - Advanced stage - 2nd view