Question
My crepe myrtles are 13 years old. A white powdery substance has been falling to the ground. There does not appear to be any aphids or powdery mildew on the tree. Now there are what looks like white worms coming out of the trunk horizontally. They do not move so I'm guessing they are not worms. How should this be treated and will it affect the plants around the trees?

Answer
Sounds like an insect called borers. What you see sticking out of the trunk is frass from the boring. Spray the trunk and other boring evidence with an insecticide called Merit. It is also known as Bayer advantage insecticide. Spray the trunk now and watch for new signs and if necessary re spray. This will kill the borer in the trunk.