The emergence of Brood X exceeded expectations in north Georgia, as those of us who happen to reside in the “cicada zone” observed droves of periodical cicadas during the peak of the event. Over the past weeks, the song of the male periodical cicada has faded and fewer of these fascinating insects remain, but a sign of their passing is still evident.
Before ending their brief life cycles, female cicadas have been known to lay eggs on over 200 types of trees, but they do have their favorites. While evergreens are rarely used for egg laying, some of the trees that are most susceptible to cicada damage include species of oak (Quercus), maple (Acer), cherry (Prunus), hawthorn (Crataegus) and redbud (Cercis).
University of Georgia entomologist Nancy Hinkle explained that periodical cicadas begin life as “a rice-shaped egg, which the female deposits in a groove she makes in a tree limb, using her ovipositor,” which is a tube-like organ many female insects use for laying eggs. The groove the female makes in the tree limb provides shelter and protects the newly hatched cicada nymph.
When the cicada hatches from the egg, it looks like a termite or small white ant. Once the young cicada is ready, which is usually just a few days after hatching, the nymph crawls from the groove and falls to the ground where it will dig until it finds the roots of its host tree, where it will imbibe fluids from the tree roots for 17 years.
These grooves can sometimes kill a tree’s small branches, and when the twigs die and the leaves turn brown, it is called “flagging.” This serves as “nature’s pruning service,” trimming off the tree’s weakest appendages, preventing them from breaking off and causing damage during the next winter’s ice storms.
Despite cicadas having a wide variety of trees from which they may choose to lay their eggs, in north Georgia, there seems to have been a strong preference for oaks and maples.
While trees showing signs of dieback or “flagging” may appear to be injured, there really is nothing to worry about. This damage is not serious, and any mature, established tree that has flagging will easily replace any shoots that have been broken or “pruned” by the cicadas. If desired, you may simply prune out any damaged branches that you can reach safely.
Across both Fannin and Gilmer counties, I noticed highly variable populations, meaning that locations with heavy flagging were often surrounded by areas with little to no flagging. While this may be somewhat normal for a 17-year periodical cicada emergence, another possible reason for the inconsistent distribution could be attributed to elimination of nymphs in those areas due to soil disturbances, such as the removal of trees — the cicadas’ food supply — and other soil disturbances. Construction and the removal of trees and clearing of forested areas can certainly have an impact on our wildlife populations and cicadas are no exception.
Despite these disturbances, nature always manages to find a way and I feel privileged that I got to experience one of the Earth's oddities. Now that the main event has passed and we’re seeing flagging, you can bet that the next brood of cicadas will soon be active underground, tunneling, feeding and growing. The Brood X cicada nymphs will stay underground for 17 years, emerging as adults in 2038.
For other questions about plant damage in your landscape, contact your local UGA Cooperative Extension agent by visiting extension.uga.edu/county-offices.