Question
I have 20 crepe myrtles on my property, and have noticed a groups of black winged ( as the insects get larger)insects on the trunks of the trees. At first I thought it was a dark patch of some sort of fungus on the trees until I got closer, and noticed the patch was moving, and that these were insects that would move apart, and then regroup in to an oval patch. When the insects are small, they look like black grains of rice, but as they grow larger, they seem to grow wings. They are not swarming, but stay grouped in these patches. Can you tell me what they may be, and how to treat them? I love my trees, and do not want to lose them to some sort of infestation. I also have magnolias, sweet olive trees, large gardenias, water oaks, and river cypresses. I do not see these insects on any of those trees of bushes. Can you help?

Answer
The most common and most damaging insect on crepe myrtles is aphids.  The bugs are soft bodied and some of the forms can be winged.  The most common location on the plant is on the undersides of leaves, so check there and see if there are small round bodied green bugs on the bottom of leaves.  Here is where they will do the most damage.  Crepe myrtle is the only plant they attack.  Control is easy with Bayer Advanced Tree and Shrub Insecticide.  It is mixed with water and poured on the soil around the base of tree.  It is taken up systemically and will kill the bugs within a week or so and provide up to 8 months of protection.  The product is sold at most big box stores.  If this does not seem to be the case, the bugs may just be transient and will probably cause no harm to the plants.  Good Luck.