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The 17-Year Cicadas are Coming: What You Should Know

March 29, 2021
Cicada

This spring Indiana will see the emergence of the 17-year cicada, also known as Brood X. These insects have been feeding underground while living on sap from tree rootsand will emerge this spring in large numbers (as many as 1.5 million cicadas per acre in some spots) to climb trees, sing, mate and lay eggs for the next brood. They will be of no harm to humans, other than a slight annoyance, will provide food for wildlife, and fortunately shouldn’t cause too much damage to the landscape, though younger trees and shrubs may be impacted (see below).

Brood X is expected to emerge throughout Indiana, though the biggest populations are expected in southern Indiana. This is because cicadas feed on trees nearly constantly, thus are found in a greater concentration in more wooded areas. The timing of their emergence will depend on temperature, but will most likely occur mid-April to mid-May, depending on the spring. We will likely get a good warning of their emergence from the southern part of the state, which will likely see them a week or two before us.

One question you might ask, if these only emerge every 17 years why do I see/hear cicadas every summer? There are different types of cicadas: a 13 year, a 17 year, and what’s known as an “annual” cicada, which is what we find every summer. Even the annual cicada has a 2-5 year lifespan, but their broods are offset to a point where we have a few each year. The 13 and 17 year cicadas are known as “periodical” cicadas, with the excitement this year being over the 17 year variety.

So how will cicadas impact us, beyond their singing? Well they do eat trees, with a slight preference for deciduous trees such as maple, fruit trees, oak and dogwoods, but can be found on just about anything. They lay their eggs on tree bark, which can create scars, and if a tree is popular enough a few twigs or smaller branches could die. Larger trees may have some dieback this summer, but usually the overall tree health isn’t affected. It will be younger trees and shrubs that may need more monitoring.

Female cicadas prefer to lay eggs on branches that are 3/16” to ½” in diameter, so if you have younger trees or shrubs and are expecting or experiencing a large emergence in your area, protection may be considered. This can be accomplished by covering tree with a mesh fabric for about a one month period then they are most active. The fabric should be draped over the twigs and branches and then secured at the bottom underneath the canopy so that the cicadas cannot climb up from underneath. Netting is preferred over insecticides, which will also harm beneficial insects that may help combat other pests later in the year. To follow cicada emergence and for more information, visit Purdue’s Landscape Report available here: https://www.purduelandscapereport.org/

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