Galls appear in different shapes, sizes and colors, depending on the insect causing them. For example, Hackberry trees are especially prone to Gall infestations caused by a psyllid insect (also called jumping plant lice) that forms a small, round bump to protect the young insect growing inside. The Galls appear on the leaf surface of the Hackberry tree. Many varieties of Oak trees are also prone to Galls.  Galls on Oak trees are primarily formed by wasp species and occasionally fly species of insects. Oak Galls appear as growths and deformities on various parts of the Oak tree, including leaves, stems, bark and flowers. Galls are formed when the insect produces a protective environment for their larvae on the host tree. Depending on the insect and host, the Gall will take on a variety of appearances.

Generally, Galls are a common occurrence on trees and plants and are not harmful to the host. There are varieties of Galls that can weaken a tree, depending on the level of infestation. Control options include pruning infected twigs and branches. In addition, there are a couple chemical treatments that have proven effective. Fertilization is also important for promoting healthy tree growth. Suspect Galls on your tree? Call the PHC Department for more information and to have a Certified Arborist inspect the tree.

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