Question
I have two trees in my eastern facing front yard that appear to have a fungus, as the trunk and branches have black areas.  They did poorly last summer and I would like to know if I could spray them before they start leafing out. The neighbors trees do not appear tp be affected. Thanks so much.

Answer
The black is a fungi called sooty mold. It grows on a substance called honeydew. Honeydew is produces by sucking insects. These insects suck the plant juices and secrete the substance high in sugar and the fungi grows on this sugar. Control the sucking insects and the black will wash off with rains. The best method of control is to use a systemic insecticide applied to the soil. The roots pick up the insecticide and carry it to the branches and leaves and when the sucking insects feed on the plant juices they are killed. One of these insecticides is Bayer Advanced Tree and Shrub insect control. It is applied to the soil under the tree. Check with your local nursery/garden type store for this product.