My crape myrtles have a black sooty coating on them. What will get rid of it? I have been spraying with something I got at the garden center. It lists a lot of things it is supposed to help with and names a fungus as one of the things , but I'm not sure if this black stuff is a fungus. I have only sprayed three times so maybe it takes a while for it to work. Should I give it more time?

Guessing it's probably the stuff called sooty mold. That's usually a symptom of a scale or aphid infestation. Both pests secrete sticky honeydew, to which the mold spores stick and are able to multiply. Aphids & scales are often placed on plants on purpose by ants, to be farmed for their honeydew. If this common chain of events is what has happened to your tree, getting rid of the ants should then relieve the pest issue & resulting sooty mold, though it probably won't wash off of this years' leaves. If CM is evergreen in your area, more treatment for the actual mold might be worthwhile/recommended. CM's are deciduous this far north.

Thank you purpleinopp. My crape myrtles drop their leaves every year. I'm hoping when they flush out again next year that this problem will have been taken care of. The ants are always a problem and I will try putting more stuff out for them.

Happy to share. Ants are the bane of my existence here too, getting the trees moldy, invading potted plants, dictating when/where I can dig around the garden, swarming inside during a downpour. Can't ever stand still w/o checking feet. Good luck fighting the good fight.

Crepe Myrtles go dormant even in zone 10 FL. Just FYI.