Protrusions Growing From the Leaves on a Tree

Leaf Galls

• Leaf galls are what gardeners often encounter when they notice protrusions growing from the leaves on a tree. Galls affect a large number of trees and plants and are the result of either feeding by an insect or a bacteria or fungus. These galls start out as bumps or distorted growths before transforming into galls of a multitude of colors, sizes and shapes, each specific to the insect that causes it or the species of plant.

Insect Galls

• A gall is the result of a chemical reaction within the leaf that spurs the plant to form a structure on the leaves or twigs of a tree. It is a collection of leaf and fungal tissue that serves many purposes. If the gall is formed as the result of feeding by an insect, the growth provides both a housing and protective structure for the insect, enabling the bug to satisfy its hunger unscathed by predators or fungicides.

Unique Galls

• Other galls develop as the result of infestation by a bacterial fungus. These structures typically serve as reproductive centers for the pathogen, emitting spores into the environment that infect surrounding plants. Gardeners may find the galls to be intriguing due to their extreme colors and characteristics. For example, cedar rust galls are fungal galls that produce bizarre-looking structures with orange horns, while jumping oak galls fall to the ground and then continue to "jump" for several days as the result of the living insect inside the growth.

Management

• Galls generally cause very little damage to the tree and are chiefly an aesthetic problem. In severe cases of infestation of long duration, the tree may begin to defoliate or lose its vigor. In these cases, fungicide may be warranted, but application methods of the chemical control must be unique to the specific type of gall in question. Most galls can simply be handpicked from the twigs or leaves of the tree as a means of management.