Issue 4, June 8, 2022
Oak Apple Galls
Developing oak apple gall, Travis Cleveland, University of Illinois
Numerous galls are found on oak trees, and almost all of them are caused by cynipid wasps. Adult cynipid wasps are smaller than pinheads and do not sting people. The largest cynipid galls are the oak apple galls, being spherical, hollow galls that mature to sizes up to 2 inches in diameter, depending on the species of cynipid and the oak host. The legless, white larva typical of cynipid wasps lives in a small, seedlike structure in the center of radiating fibers that extend to the inside edge of the gall. Although they are initially green, oak apple galls mature to tan galls with a hard, papery exterior. Although the galls are common and easy to see, they are seldom important enough to need to be controlled.
Split oak apple gall, Travis Cleveland, University of Illinois
Mature oak apple galls with exit holes, Travis Cleveland, University of Illinois
Author:
Travis Cleveland