Question
I have always had to spray my crepe myrtle trees in the summer because the beetles love them.This past year over a period of a month the leaves had this thick black coating on them that was terrible.What is that?And what can I do to prevent this from happening this year?

Answer
The black is sooty mold that grows on Honeydew that is produced by aphids, an insect. Aphids are small soft bodied insects that suck the plant juice and secrete a liquid called honeydew, which is high in straches. A sooty mold will then grow on this honeydew. Control the aphids and you will control the black coating. I would start spraying  after the tree has leaved out and spray once a month for a few months. This should kill early insects and keep the population from buildning. I would check with a local garden type store and use a systemic insecticide for aphids. The plant will take up the systemic insecticide and the effect will last longer.