Eddie’s Corner: Alien Leaves…Leaf Galls on Trees

By Eddie Ayers, County Extension Agent

Leaf Gall 2Several unusual leaf samples have been delivered to the office this spring. At first glance it looks like a possible invasion by a new alien plant or disease, but in reality it’s just a leaf gall, the result of an insect. Most galls develop during the spring and early summer each year. Very unusual shapes and colors of newly formed galls often get someone’s attention if they have never seen one before. The leaves have something that look like bumps or horns or tubes sticking out of them. Even though you may see odd or strange leaf colors as well, they are still productive and will stay on the plant for a long time. 

Nearly everyone has seen an insect gall on trees or other plants even though they might not realize it. Galls are abnormal vegetative growth resulting from the work of insects, usually immature, and other organisms. Several hundred different kinds occur on trees. Leaves are most commonly infested but some also occur on limbs, fruits, and roots of trees and on many other plants. Some kinds of galls occur almost every year on the same tree or plant but the majority of galls do not occur on a regular basis. It may be ten years between infestations of some gall problems on trees, and there is no known way to predict when gall infestations will occur. Most do not kill the host. They only reduce the aesthetic qualities.

There are so many different colors and shapes because they can vary depending on the tree type. The oak felt gall which develops on oak leaves has a bright red color. A gall that occurs on the leaf and petiole of hickory, walnut and pecan trees is commonly called pecan phylloxera. When this gall is present in large numbers, they distort leaves as they develop causing a very unnatural appearance on the tree. Sometimes maple leaves are infested with many small reddish colored galls which are called maple bladder galls. Although unsightly, they don’t seem to do any significant damage to the tree. The leaf tissue between the galls is healthy, continues to grow, and produces food for the tree.

The biology and identification of many galls has not been studied and developed, however it is reassuring to know that most galls do not seriously affect oak, hickory and maple trees, therefore treatment is not necessary. And since they are not of economic importance, chemical controls have not been developed either. It is believed that parasites, predators or adverse environmental conditions reduce potential infestation problems. And picking up the leaves and removing them from the area may help lessen the infestation next year.

While I have your attention, I’d like to mention several functions we have going on this summer. First, we’ve extended the deadline and are still taking applications for a Master Gardener Extension Volunteer Class that starts in August, but the deadline to apply is June 30. Also, the current Master Gardener Extension Volunteers host the Ellijay Farmers Market on Broad Street adjacent to the Gilmer County courthouse every Saturday morning from 8 am to 12 noon so come check out what the local farmers, crafters, honey growers, jelly, jam and soap makers have to offer. And the Gilmer County 4-H Club is selling tickets to Six Flags and White Water as a fundraiser for their programs so if you or someone you know is planning to visit one or both of these parks, support your local 4-H Club. For more information on anything mentioned here, contact me in the Gilmer County UGA Extension office.


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