Question

1093.JPG   Attached is a picture of a growth on a young white birch tree.  The tree is approximately 4' to 5' tall and located in Sioux Lookout, Ontario, Canada.  There are 2 of these growths on this tree, both near the top, growing out like a leaf stem would.  Do you have any idea what this is and/or what is causing it?

Thank you,
Karen Perreault

Answer
Strange bumps or growths often appear on leaves of trees and shrubs. These are usually leaf galls. Although they may look like a serious problem, most are harmless to the overall health of the tree or shrub.

Leaf galls are fairly common on trees and shrubs. A gall is actually plant tissue that has developed as the result of feeding or other activity of insects or mites. Sometimes it is the result of an insect laying eggs on the leaf and the leaf cells form the gall. Plant hormones are involved when the pest interferes with leaf development in the spring.

Once the gall appears on the leaf, there is no way to control it. Preventing most leaf galls is extremely difficult. However, other than being unsightly, most leaf galls are not harming the tree or shrub. It will not harm the tree and will drop off with the leaf in the Fall. Galls are not really a problem unless they completely cover most of the leaves. Then it only causes growth loss for that year.  Not anything that you need to worry about.