Ornamental & Tree Diseases

What are the patches of crusty, greenish-gray growth on the bark of my azaleas, camellias, and lower branches of shade trees in my yard?

Sounds like you have lichens on your plants. Lichens are unique creatures in the plant world, since these patches are actually composed of two organisms (an algae and a fungus) living in association. The appearance, however, is that of a single plant. Homeowners often become concerned when lichens showup on plants and think they're causing damage. Not so! For more information on lichens and their relationship to the health of your landscape plants, refer to a Plant Pathology Infobytes Newsletter on this topic.