Photos might help.
Identifying molds, fungus and bacterial infections from photos is "iffy", but we try.
Generally fungi and bacterial problems are signs of horticultural conditions not being idea. Usually not enough air movement. If the tree is on the ground, and especially if the tree has other plants crowding around it, it is not enough air movement. Put the tree up on a bench, or a plastic milk crate, or even a large rock, to get it up and off the ground so that it gets more air movement.
Similarly, fungi and bacterial problems can be a sign of excess moisture, watering too frequently or a potting media that is not draining adequately.
It will be up to you to determine if it is a water issue, or an air movement issue.
Simply improving the growing conditions is often all that is needed to get fungi and bacterial issues to clear up. Sprays are not always necessary. Prune off affected wood, and set in the improved growing position.