We have tree azaleas that the branches are turning black color with a black powder residue that falls to the ground. There are also white looking (I think) powdery spots on the branches. Is this treatable?
Diseased Tree Azalea
Certified GKH Gardening Expert
This is sooty mold, usually caused by pests--in this case probably azalea bark scale. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/shrubs/azalea/azalea-bark-scale.htm
I would treat the shrubs with neem oil, which should take care of the sooty mold as well as the pest. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm