ARNOLD AIR FORCE BASE, Tenn. -- Across Arnold Air Force Base during late spring and early summer, you may have noticed our hardwood trees with dry, wilted or dead-looking branch tips.
A swath of the eastern United States from New York to Georgia has millions of trees that look the same. The phenomenon is called “flagging,” and it is caused by cicadas.
This year, Tennessee was visited by more of the insects than any other state.
Cicadas emerge from the ground in what is termed to be a “brood.” This year’s group was Brood 14, and it has a lifecycle that has it only above ground every 17 years.
Brood 14 is the largest of the 17-year type.
Once above ground, the cicada will only live for four to six weeks. During this time, they will grow into maturity, find a mate by making a lot of noise, mate, lay eggs in the branches of hardwood trees and then die.
The adult cicada will make grooves in the underside of the tree branch in which to deposit eggs. On most occasions, this action causes the branch to die.
For the tree, it amounts to being pruned. New tree growth will start at each flag.
The eggs will develop in the branch of the tree this summer and, once ready, a young cicada will emerge, fall to the ground and dig deep under the host tree to live the next 17 years consuming sap from the roots.