17-Year Cicadas Return

People are starting to ask us about the cicada hatch that has begun.  Maybe you’re one of the lucky folks whose landscape has been invaded by this year’s brood of 17-year cicadas and are worried about their effect on your plants (and sanity).  Here are a few facts to help you deal with them.

 

17-Year Cicadas-Brood II distribution. Click to enlarge.

The 17-year cicadas (with the cool species name Magicicada) have spent the last 17 years underground as nymphs, quietly feeding from the roots of deciduous trees.  They are distinguished from the annual cicadas that appear every summer by their red eyes and orange wing veins.  Every member of the brood emerges from the ground over the course of just a few days, making for massive numbers in the areas that they populate. There are several broods active in North Carolina; this year we are treated to Brood II (nicknamed “East Coast Brood”).  Other expected brood years are 2017, 2019, 2020, 2021, 2024 and 2025.

Shed cicada skins

They began emerging in this area in early May, 2013.  They are very localized and patchy in their distribution, meaning your neighbor’s trees (and house and patio) may be overrun, while you hardly notice them.  You probably don’t have to wonder if they are in your trees or not; where they emerge their numbers are staggering and you will notice them.  

They do not bite or transmit any diseases to plants or people, although, very rarely, they may mistake you for a tree and try to suck your sap. On the off chance that this happens, they are not venomous and will cause no harm besides the “ouch!”

The males are the only ones who “sing”, and don’t start for several days after emerging.  They can reach up to 90 decibels if you’re standing close to a tree full of them. 

 

 Cicadas’ primary purpose after emerging is to meet the love of their short lives and reproduce.  During the 4 to 6 weeks they live, they feed on plant sap from woody plants.  Though they may be observed on non-woody plants like perennials and flowers due to their sheer numbers, they do not feed on them.  Generally they do not cause excessive damage during feeding, especially on mature, established plants.  Females laying eggs can cause tips of smaller branches to die back.  Blocking cicadas from weak trees and shrubs with netting, or spraying them off with jets of water may be moderately effective (you’ll have to spray water very frequently-they will just fly back).  Few insecticides are very effective against them, and due to the fact that many dogs and cats and birds enjoy eating them and could potentially be poisoned by the residual pesticides it is not recommended.  Cicadas do not feed or lay eggs on pine trees and other conifers.

Cicada emergence holes

So what’s to like about them?  You’re getting some free lawn aeration from their emergence holes if they are heavy in your area.  Birds (and squirrels, believe it or not) like to eat them, so you’ll probably see plenty of feathered friends if you have a large cicada population. As loud as they can be during a warm day, fortunately they go silent at night.  Almost the entire 17-year brood should be gone by July….just in time for the annual cicadas to emerge.