June 7 2021 09:17 AM

Find out what landscape professionals need to know about the cicada invasion.

It’s not uncommon to hear a few cicadas out during the summer, but this year there’s much more of a racket. The Great Eastern Brood Cicada, also known as Brood X or Brood 10, has been pushing their way back above ground after 17 years and putting additional strain on the landscape.

“These are not the annual cicadas that we are all used to seeing,” says Jonathan Larson, an extension entomologist at the University of Kentucky. “The Brood 10 Cicadas are below the ground anywhere between 13 and 17 years, whereas the annual cicadas are below ground between one to three years. The problem is when they come up in huge numbers they can cause major damage to newer, younger trees in a landscape. It is one of those things that is not on the radar until it is. Since it only happens once every 17 years it is not on the mind of landscapers as something to be preparing for.”

The appearance of the Brood X Cicada occurs when the soil at eight inches deep becomes 64 degrees, which also happens to coincide with the full blooming of irises in a landscape, says Larson. A longer winter weather season delayed the emergence of the cicadas, which occurs over a six-week period that ends in June. This means that the month of July needs to be totally dedicated to defending younger trees against cicadas.

There is a reason this species of cicada is called the Great Eastern Brood as its presence is mainly limited to the East Coast, says Larson. They will have a heavy presence on the eastern border up to Pennsylvania and New York City, and deep into the Midwest and upper South to Indiana and Kentucky. An additional group of the species is anticipated on the river corridor in Nebraska, but that is as far west as the Great Eastern Brood Cicada is expected to appear.

“It is very much an eastern phenomenon,” says Larson.

Taking care of the trees

Of the various types of trees that cicadas lay eggs in, their favorite are fruit, maple and oak trees.

“The Brood Ten Cicada is attracted to the tree itself because the female wants to lay eggs in trees,” says Larson. “There are over 80 different species of trees that they can lay their eggs in, so this is a really relevant issue for landscaping companies both big and small.”

Cicadas make a slit in a tree and lay two dozen eggs at a time, and with a total of 200 eggs, the process can take an immediate toll on a young tree especially when it's left unprotected, says Larson.

“The best thing for landscapers to do to protect against cicadas is to invest in cicada netting and put it on and around trees,” says Larson. “Use the landscape netting for up to eight weeks or maybe even a little bit longer to exclude females from getting in the three and laying their eggs.”

While some recommend using insecticides on trees before or during the appearance of cicadas, Larson strongly disagrees with that tactic.

“That can be hazardous for trees and end up causing more harm than good,” says Larson. “Stick to netting, physical exclusion is always the best strategy.”

But what if you get a late start in your defense against cicadas? You still have time to win the battle, according to Larson.

“Once you start hearing them, it is time to put the netting out,” says Larson. “If you missed a few it is okay, but if they are already deeply infested in the tree, it might be time to focus on nursing the tree back to health and not on the netting.”

Larson advises landscapers to be as proactive as possible against pests, including building a calendar of when and where pests are going to appear in their region. He also advises landscapers to do as much scouting and research as possible at new properties from the start and try out different traps to see which ones are most effective.

“It is a grind to do it at the start, and it takes a lot of time, but in the long-run it is going to save landscapers energy, time and money,” says Larson. “If you have a calendar already completed, then nothing should catch you by surprise.”