As leaves beging to change and fall, you may start seeing more of these weird round balls attached to oak leaves. They're not uncommon and yet remain somewhat mysterious. So what the heck are they?
They're galls, specifically, leaf galls. The one you see above is most likely an oak apple gall. Galls can form on both the leaves and wood of a tree, come in a variety of shapes and sizes, and some are even fuzzy. A gall is an abnormal growth on the outside of a plant that occurs because something is irritating the plant, such as an insect, fungi, bacteria, or parasite. The oak apple gall is caused by the larvae of a wasp called, appropriately enough, the oak apple gall wasp.
An oak apple gall forms when a female wasp injects an egg into the leaf or a developing leaf bud. Upon hatching, the larvae produces a chemical that irritates the leaf. In response, a gall forms from the leaf tissue and surrounds the wasp larvae. The gall protects the larvae as is grows and develops, eventually pupating within the confines of its spongey globe. Once it emerges as an adult, the wasp drills its way out of the gall.
Don't worry, though! Oak apple galls are essentially harmless and do not impact the health of the trees. Oak apple wasps also can't sting, so they are of no danger or discomfort to humans - always a plus for woodland explorers.
An oak apple gall forms when a female wasp injects an egg into the leaf or a developing leaf bud. Upon hatching, the larvae produces a chemical that irritates the leaf. In response, a gall forms from the leaf tissue and surrounds the wasp larvae. The gall protects the larvae as is grows and develops, eventually pupating within the confines of its spongey globe. Once it emerges as an adult, the wasp drills its way out of the gall.
Don't worry, though! Oak apple galls are essentially harmless and do not impact the health of the trees. Oak apple wasps also can't sting, so they are of no danger or discomfort to humans - always a plus for woodland explorers.
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