– Christine Gelley, Agriculture and Natural Resources Educator, Noble County OSU Extension
Galls can appear on nearly all tree species.
Last week I had the opportunity to visit Punderson State Park up in Geauga County for our annual Agriculture and Natural Resources (ANR) Extension Retreat. During this event, ANR Educators, Specialists, and Staff get together to learn from each other in an environment out of our normal stopping grounds. The time spent together creates unity within our team while also expanding our appreciation for the diversity of Ohio’s agricultural and natural landscapes. The first activity I participated in at ANR Retreat was a woodland diagnostic nature walk around one of the trails that begins at Punderson Manor.
We did far more talking than walking. It was a good thing we had three hours to walk the trail, because almost every step we had something new to look at and discuss. One of the most common things that caught our eyes were galls. There were galls galore along the trail!
What are galls?
Galls are abnormal growth on plants that have various causes. Galls can be the result of fungal or bacterial infection, insect development, or cell mutations. They vary in size, shape, and color. Some of the most interesting and bizarre looking galls are caused by aphids, sawflies, mites, and wasps, but in almost all cases, they do not threaten the overall health of the host plant. Most of the galls we saw on our hike were caused by wasps.
Friday morning after returning from Punderson, I went out with a client to take a look at some blue spruce trees experiencing needle loss and along the way, saw something familiar on a passing maple. They were galls.
One of the most common galls that I see are thin spiky galls on the leaves of maple trees. Instead of a wasp, these galls are caused by the maple spindlegall mite. We have a fabulous fact sheet available from OSU Extension called “Galls of Maple Trees in Ohio” written by two OSU entomologists- David Shetlar and Jennifer Andon, that I regularly share with people concerned about galls and use to confirm identification in the field.
According to the fact sheet:
“The abnormal plant growth is stimulated by a combination of plant hormones and hormones introduced into the plant during arthropod feeding. The plant responds by increasing the production of leaf tissue, thereby enclosing the individual mite or insect. The enveloped arthropod feeds and reproduces from within the gall… Homeowners often become quite alarmed when they discover that their maple tree leaves are infested with leaf bladder, spindle, erineum or gouty vein galls. They fear that the tree is going to die unless something is done quickly. This is not the case. Maple leaf galls seldom, if ever, cause permanent injury to a tree, but they do detract from the beauty of the leaves.”
Galls can impact practically all tree species and varieties and should be appreciated for the interest they add along with the insect diversity they promote in our ecosystem. Occasionally, galls may cause early leaf drop on deciduous trees, but they do not cause enough damage to stress the tree or prevent future growth.
Galls are fascinating and I am always intrigued when I find them. If you find a gall in your landscape and are curious about what caused it, send me a picture and description and we can figure it out together! Email me at gelley.2@osu.edu with your location and contact information.