Periodical Cicadas, you probably have seen the giant insects with bulgy red eyes and see through wings, shedding their skin and clumsily flying through the air. These insects emerge by the billions every 13 to 17 years and can cause temporary and lasting damage to trees.
The Cicadas currently plaguing the DC Metro area surprised us and rose from the ground 4 years early. Brood X, the name for this group of Cicadas, was predicted to rise from the ground in 2021, 17 years after their last emergence in 2004.
Researchers say it’s typical for a few Cicadas to get confused and rise early; however, this large of an emergency is surprising and may have other causes. Entomologists have theorized that climate change, specifically warmer springs, may be throwing off the Cicadas ability to count the years.
Either way, Cicadas are here to stay and damage our trees for the next 6 weeks. Learn how the damage occurs, what trees are at risk, and what you can do to mitigate the effects.
Cicadas spend their first 17 years underground feeding on the roots of trees and developing into mature nymphs. In May of the 17th year, they emerge from the ground, to shed their exoskeletons and mate. You are probably familiar with their loud mating calls resembling a high-pitched whine.
About 10 days after you first hear the Cicada chorus the females begin laying their eggs, which is where the damage comes from. Females rip into the branches of trees to lay their eggs under the tree’s bark. Within about a month females lay up to 400 eggs in 40 to 50 pockets under the bark of trees.
Laying eggs in this manner commonly causes the stem beyond the egg pockets to die. Sometimes you may see these branches break and fall to the ground but typically the branches’ leaves wilt and turn brown, a symptom called flagging.
When a tree goes through this type of repeated damage it can become stressed. Stressed trees are likely to become unhealthy and are more susceptible to disease and insect attacks. To compound on this, the rips Cicadas leave in the tree’s bark are open wounds which act as entry points for these insects and diseases.
Between flagging, stressing the tree, and leaving entry points for harmful insects and diseases Cicadas pose a threat to the health of your trees.
What Trees Are At Risk?
Preferred host trees of periodical cicadas: elm, chestnut, ash, maple, and oak.
Small or ornamental trees, specifically trees 4 feet and under, have the highest risk of dying from Cicada damage. In these cases, the tree usually cannot sustain itself after it’s had the majority of its branches killed off by Cicadas laying eggs.
Healthy trees over 6 feet tall will not be significantly affected by Cicadas laying eggs. However, they can become stressed and develop insect or diseases complications because of the wounds left behind by the Cicadas.
What Can You Do To Help Your Trees?
Netting For Small, Newly Planted Trees: If you have a newly planted tree under four feet tall you should make sure to protect it from Cicadas using netting. Drape the netting over your tree and fasten it securely around the trunk so bugs can’t crawl up underneath.
Don’t Attack Them With Pesticides:
Pesticides do not effectively manage Cicadas. Pesticides also rid your tree of beneficial insects which would help prevent your tree from harmful insects and diseases in the future.
Give Them Some Extra TLC After Cicada Season:
Fertilize: First of all, to help your tree overcome the stress and damage caused by Cicadas you want to promote root growth and make sure your tree has the nutrients it needs.
Post-Cicada Pruning: Removing the deadwood created by Cicadas will help your tree look better and stay healthy. Also, pruning within 6-7 weeks after Cicadas lay eggs (before they hatch) will reduce the Cicada population in your landscape making the next emergence that much easier to manage.
Keep Them Hydrated: In order to recover and not contract any other diseases make sure your tree doesn’t experience any additional stress from drought. Make sure the keep them watered throughout the summer and hot days of early fall. Check out our watering tips.