Periodical cicadas: You probably remember seeing these giant insects in 2004, with their black bodies, bulgy red eyes, and see-through wings, shedding their skin and clumsily flying through the air. And you likely heard them making noises at night while you were trying to fall asleep.
Every 13 to 17 years, periodical cicadas emerge in the various regions of the United States and can cause temporary and lasting damage to trees. This year, Brood X will be crowding the Northern Virginia, DC Metro area.
2017’s Surprise Emergence:
In 2017, we were all surprised by the Brood X cicadas that plagued our area. Most individuals didn’t expect them, as they typically make their emergence every 17 years and had come four years early.
Well, it’s finally 2021, the year for Brood X. So, what can you expect?
Here’s the good news: cicadas won’t bite or sting you. It has also been predicted that suburban areas with recent construction are less likely to experience a massive emergence.
Here’s the bad news: when these insects do crowd your area, the female cicadas will likely leave damage on your trees.
To help you prepare, we’ve put together a guide on periodical cicadas. We’ll discuss their life cycle, how they might damage your trees, which trees are at risk, and what you can do to mitigate the effects.
What is the 17-Year Cicada’s Life Cycle?
Unlike annual cicadas who only spend two years underground, periodical cicadas live underground for their first 17 years, feeding on tree roots and developing into mature nymphs. At just the right soil temperature (~64ºF), adult cicadas come above ground to shed their exoskeletons and mate. Then come the loud mating calls we are all familiar with.
About 10 days after you first hear the cicada chorus, the females begin laying their eggs, which is when the tree damage comes in.
Female cicadas 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.
How Do Cicadas Damage Trees?
Trees may experience damage during the egg laying process, as the female cicada lays her eggs under the tree or branch bark. Laying eggs in this manner commonly causes the stem beyond the egg pockets to die. This tends to result in broken branch ends and wilted leaves: signs that flagging has occurred.
When a tree goes through this type of repeated damage, it can become stressed. Due to the stress and ripped open tree bark, the tree becomes more susceptible to disease and insect attacks.
Younger Trees: The bug may bring slightly more risk to younger trees, especially if they are ornamental fruit trees. Female cicadas are more drawn to smaller trees, as they are more driven to lay their eggs on their branches.
Older Trees: Mature, established trees are stronger and are easily able to recover from the loss of branch ends.
Fortunately, overall, the tree bug bears little damage on a landscape. The issues the insect presents are mainly cosmetic and should cause little to no worry.
Are Cicadas Dangerous To My Trees?
As the damage cicadas leave on trees is mainly cosmetic and poses little overall risk, these flying insects are not considered pests and do not kill trees. They come for the sole purpose to reproduce and are gone within a few weeks.
Still, you may want to be on the look-out to make sure your trees are safe from the emergence this year.
Here are the trees most susceptible to cicada damage:
Preferred host trees: elm, chestnut, ash, maple, and oak.
Small or ornamental trees: Small, young trees, especially those 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.
NOT healthy trees over 6 feet tall: Healthy, older trees will not be significantly affected by cicadas laying eggs; however, they can become stressed and might develop insect or disease complications because of the wounds left behind by the cicadas.
How Can I Protect My Trees From Cicada Damage?
While you can’t entirely get rid of cicadas, you can try protecting your landscape from them.
Hold off on planting new trees: If you’ve been wanting to add new trees to your landscape, we recommend waiting until after cicada season, in the fall, as younger trees are most vulnerable to damage.
Netting For Small, Newly Planted Trees: If you have a newly planted tree that is under four feet tall, you can try to protect your tree with netting. To apply, drape the netting over your tree and fasten it securely around the trunk. When done properly, you can potentially prevent bugs from crawling up from underneath it.
Note: Netting is known to fly off trees and might lead to foliar diseases if left on too long. If netting is used, we recommend leaving it on only during the egg-laying period (the only period the tree is really susceptible to damage). An easy way to identify that the egg-laying period is over is if you stop hearing cicada buzzing!
Don’t Attack Them With Pesticides:
Pesticides do not effectively manage cicadas. On top of that, as an environmentally friendly company, we don’t recommend pesticides as they are not eco-friendly. Pesticides rid your tree of beneficial insects that prevent your tree from harmful insects and diseases.
Give Them Some Extra TLC After Cicada Season:
Bio-stimulants: Biostimulants are often the #1 recommendation our Certified Arborists give to homeowners. They’re the all-natural, organic multivitamin for your plants that can help bolster your trees’ overall health by making sure their roots have all the nutrients they need. Naturally, they are apart of our annual Canopy Protection Program, also known as our total tree & shrub care program.
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 they lay eggs (before they hatch) will reduce the population in your landscape. This helps make the next emergence 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. Be sure to keep them watered throughout the hot days of spring, summer, and early fall. Check out our watering tips.
Editors Note: This post was originally published in May 2017 and has been updated for accuracy and comprehensiveness.