There are many varieties of scale that infect shade trees and shrubs. They are sap-sucking insects that are very difficult to control and they can go undetected until extensive damage develops. Armored scales look like little globes and have a hard shell. Soft scales secrete honeydew and they look like little bumps on the branches. There are hundreds of varieties of scale insects. They start off as tiny crawlers the size of poppy seeds. As adults, they fix themselves and feed on a single spot in clusters along the limbs of trees and shrubs. Fruit trees and ornamental trees are often affected and require immediate attention.
Symptoms: Light shaded bumps or round flattened shells cluster along the limbs. Soft scale insects cause honeydew drips on cars, driveways, paths, and furniture under the infested trees. Ants and wasps may be attracted to affected trees by the honeydew.
More information: Purdue University Extension Entomology, University of Minnesota Extension
Photo: NC State University / University of New Hampshire