Redbud Tree Bugs

Scale insects are common pests of redbud trees.

Eastern redbud is also known as "Forest Pansy" and is a member of the Fabaceae family. This tree grows rapidly, typically reaching heights of 20 to 30 feet, and produces lovely pinkish-purple flowers in the spring. Eastern redbud is typically healthy, but is susceptible to insect infestations which damage its health and vigor.

Types

Scale insects are often seen on redbud trees. This insect is 1/16 to 1/4 inch in diameter and has a waxy shell covering its body. This shell protects the bug from insecticides and predators. Scale insects feed on sap from the leaves of the host tree and are typically difficult to control. The fall webworm is another damaging pest of redbud trees. In its adult form, the fall webworm is a moth that lays its eggs on the undersides of redbud leaves. The larval form of this pest is a caterpillar that measures approximately 1 inch in length. Fall webworm moths typically have four generations each year, resulting in extensive damage to host trees.

Effects

Scale insects feed on redbud leaves with their piercing mouthparts, extracting plant sap. After extracting plant sap, these bugs produce honeydew, a very gooey substance. Honeydew adheres to the surface of redbud stems and leaves, causing sooty mold fungi to stick there. Sooty mold is characterized by a thick coating of gray or black fungal spores that cause host trees to become unattractive. Fall webworm feeding causes redbud trees to develop a ragged appearance. Most damage is limited to a specific area on the tree. However, several generations of fall webworms on the same host tree can cause significant damage to the foliage.

Cultural Control

Light infestations of scale insects are easily removed by hand or by placing a cotton ball soaked in alcohol on the insects and removing them. Washing your tree with a soap solution of 1 quart water and 1 tbsp. liquid dish soap may also kill scale insects. Fall webworm can be hand-picked from host trees while in the caterpillar stage. Remove or prune out nests in your tree and crush them. Heavy infestations of this pest often requires chemical control methods to prevent serious injury to host trees.

Chemical Control

Insecticidal soaps are available at your local garden supply center and often remove stubborn scale insects. These products must come into contact with scales, and applications must be repeated for continued control. Fall webworm infestations are often treated with insecticidal sprays containing Bacillus thuringiensis (Bt), or Bt soil drenches may also be effective in controlling fall webworm caterpillars.

References

• MOBOT: Cercis Canadensis Forest Pansy
• Iowa State University: Houseplant Scale Insects; Iowa Insect Information Notes
• Ohio State University: Fall Webworm Management; David J. Shetlar