Beware of Brood X

A cicada nymph newly emerged from the soil will soon shed its exoskeleton to become an “adult.” (Photo used courtesy of Jeff Volter.)

Cicada advice from The Cov’s urban forester on eve of ‘invasion’ 

COVINGTON, Ky. – The invading horde called Brood X will soon emerge from its 17-year-old underground hiding place.
But whether you see cicadas as a protein source or a mini version of the Graboids from “Tremors,” the cyclical version of Cicadidae poses only a minor threat to your trees (and zero threat to your flowers and vegetables).
That’s according to City of Covington Urban Forester Cassandra Homan, who wants to perhaps calm a few anxieties about the beady-eyed insects that are expected to emerge by the trillions in the next couple of weeks.
“With all the hype surrounding this 17-year cycle, you’d think we’re about to enter a real-life horror movie, but the reality is quite a bit less traumatic,” said Homan, who works for the Public Works Department. “Cicadas are loud but more annoying than scary – for example they rarely bite and generally aren’t attracted to homes -- but they can cause damage to young trees.”
With that in mind, Homan is offering a few thoughts:
  • Periodic cicadas (those that emerge on cycles) are generally not “tree killers,” but females can cause damage to twigs during the egg-laying process.
  • For mature and healthy trees, this “damage” is typically not a big deal and may even stimulate growth of fuller canopies by simulating “natural” pruning.
  • However, young trees and small, ornamental trees or fruit trees are at higher risk because most of their “branches” are twig-size.
  • One option is to cover valuable trees with protective netting during the heavy parts of the infestation period. If netting is too expensive or difficult to install, you can also just wait it out and hope for the best. Again, die-back is usually minimal.
  • (Given the sheer volume of streetscape trees in Covington, the City is taking the “wait it out” approach, Homan said.)
  • DO NOT attempt to treat cicadas with pesticides. This is ineffective at best and will kill off helpful insects.
  • If you haven’t already ordered new trees for a spring planting, consider postponing planting until fall. Fall is just as good a time for tree planting as spring (some argue better even).
  • Cicadas don’t really affect flower or vegetable plants and also typically avoid evergreens.
  • Periodical cicadas can be a helpful part of a thriving ecosystem: As larvae, they can help with root development by providing soil aeration via tunneling. In addition, both adults and larvae are consumed by a wide variety of wildlife. 
The good news is that the invasion is only temporary, Homan said.
“There are three different species that make up this brood, so you might see the population ebb and flow a little, but they should be mostly done by July,” she said.
In the meantime, if you want more information about cicadas, see WVXU’s 10-part series with Dr. Gene Kritsky (and a podcast link).
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