In the early spring, the surfaces of the tree leaves develop small spherical growths called galls. The small special growths are often a light yellow, green, red, or brownish colour and are normally on the top surface of the leaves. Depending on the variety of gall, they can be created as a egg nest or be the result of a toxin injected into the leaf.
Leaf galls are identifiable by small round balls or bumps that grow on the leaves, twigs, and leaf stems of trees. They can also appear as a wide variety of abnormal growth in a variety of shapes on the leaves, twigs, or branches. Infected branches may be discoloured or distorted and drop prematurely. In some cases, the infected branches die.
In many cases, Galls are created by tiny mites or other insects that bite into the underside of the leaf and then inject the leaf with a growth promoting substance that creates the spherical shaped growth. The circular ball or gall encloses the mite and the female mites lay their eggs in the gall.
Recommended Steps to Control Galls
Once the gall is formed, there is no way to eliminate the balls in the current growing season, however, to help control gall outbreaks, severely infected branches can be removed. Branches and leaves that fall to the ground should be collected and removed.