I am growing a number of varieties of citrus here in this very wet climate, and I'm noticing that different types have different resistance to fungus. With the oranges the worst by far is Washington Navel. Valencia is next along with Malaguena. Pina and Temple seem to be somewhat better. Dancy and Clementine Tangerines are pretty good, but Orlando Tangelo seems to have problem. The grapefruits seem to take care of themselves.
The best citrus trees I have are the Ortantique. There is very little evidence of fungal problems, or, for that matter, is there a problem with the black bees which do a number on the orange trees.
I don't like to spray, even with soap and H2O2 (I'm a lazy retiree, gacias adios). I would be interested in others' experiences here.