to NGA
You do have ants and that black stuff could be sooty mold. It grows on the excretions of sucking insects. The ants are attracted to the sooty mold. Some flying sucky-bugs could be at the heart of the whole problem.
But, the sucky-bugs would also be causing damage to the leaves and I don't see any. It doesn't look like powdery mildew either. Are you having a wet, warm and humid summer?
Besides seeing ants, black stuff and something flying around, do you see any damage to your plant?
Maybe it just needs a good hosing off.
