Sick Crepe Myrtle
Hello there, I have a 10 year old crepe myrtle that is dying. The leaves have a black color, the bark is turning black, the leaves are falling prematurely and very few small blooms. This tree has been very healthy up until this year. I read about a condition called sooty mildew. Please advise. Thank you, Cookie Maxfield Pictures attached
We viewed your photos. It looks like they were subject to a sucking insect called aphids. They excrete a honeydew as they feed which promotes the growth of a black sooty mold. The damage is most likely done. You can try hosing off the foliage with water however, sooty mold is difficult to remove.
It is common for bark to exfoliate on crape myrtles. We also notice possible lichens on the trunk. They are not a reason for any decline. http://extension.umd.edu/hgic/lichens-trees-and-shrubs
Next season, monitor for the aphids. It is possible that predators and parasites will control naturally. If there are no predators or parasites controlling the aphids and you are noticing damage, spray with a summer rate of horticultural oil or neem oil. Follow label directions and do not spray in high temperatures as it can damage the foliage.