Question
I have several Crypt Myrtle trees that are around 2 years old and there is now a black fungus (I believe) on all of the trees and the perennials I have on the ground underneath them, it is on everything around these trees now.  Can you give me advice on what to use to remove this.  Thank you.  I await your reply.

Answer
This is called sooty mold. The problem is really an insect called aphids. These soft bodied insects suck the plant juices from the leaves and excrete a substance called honeydew. The honeydew is high in sugar content and tends to be sticky. The sooty mold is growing on this honeydew. Control the aphids and the sooty mold will be controlled and will wash off with the rain.

There are many insecticide that if sprayed on the foliage of the tree will control the aphids.

Chemical Control - Contact Insecticides Numerous contact insecticides are registered for aphid control. Since aphids are often placed under considerable pesticide pressure in field crops and greenhouses, they may be resistant to certain categories of insecticides. Therefore, if you do not obtain reasonable control, consider rotation to another insecticide. Contact insecticides currently registered for aphid control include: acephate (Orthene), , bifenthrin (Talstar), chlorpyrifos (Dursban), , diazinon,  lindane, malathion, nicotine sulfate, pyrethrum, rotenone, resmethrin, and tetramethrin + sumithrin.

Chemical Control - Systemic Insecticides Several systemic insecticides are useful in aphid control. Aphids have sucking mouthparts and are thus very susceptible to pesticides located in the plant vascular system. Some of the systemic insecticides also have contact activity. Systemics injected or applied to the ground are less harmful to beneficial insects. Systemic insecticides include: acephate (Orthene), others that are restrictive use pesticides.

Check with your local nursery fro an insecticide for aphids on trees.