Order: Hymenoptera, Family: Cynipidae
You may have seen these tan-colored, one to two inch diameter balls laying on the ground under red oak trees this spring and wondered what they were. Oak apples are actually galls caused by small, plant-parasitic wasps. Pick one up and it will feel light and hollow, like a ping-pong ball. Break into it and you will find it filled with a light spongy material, and there will be a hard, pea-sized kernel in the center. Cut into this kernel and you may find the larva or pupa of the insect that caused the gall to form. Galls usually form on the midvein of leaves, dropping to the ground when mature. In this photo you can see the small BB-sized hole through which the mature wasp emerged. Oak apple galls are not especially harmful to the tree. Occasionally a tree will bear an especially “good crop” of oak apples, but oak apples are rarely so abundant that they are easily spotted earlier in the year as they are developing on the leaves. Later in the year, it is sometimes possible to see large oak apples while they are still on the tree. Children enjoy playing with oak apples and sometime use them in craft projects.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.