“All good things must come to an end” and that includes the cicada emergence of 2014. Most of us will be sad to see them go, though many living in the midst of the emergence will be relieved that the cacophony of cicada singing will soon be over.
The adults that began to emerge in the last week of May are starting to die of old age after their brief 4 weeks above ground. But before they go, the females lay their eggs in the twigs of a wide variety of plants (more than 75 species of trees and shrubs!). Photo 1 below shows a female cicada in the process of inserting eggs into a stem. The ovipositor (egg-laying organ) originates from about the middle of the female's abdomen. Each female lays up to 400 eggs by inserting about 10 eggs per slit into as many as 40 to 50 slits. The eggs are fairly deep inside the twigs and stems with a double row of eggs, one on each side of the slit. (Photo 2)
The egg-laying process produces scars that resemble hail damage but are more slit-like and splintered. Photo 3 below shows numerous egg-laying scars on an aronia plant stem. Within days of egg-laying the twigs start to dry out and die. The twig die back, called flagging, can be seen now on many trees and shrubs.
Healthy, well-established trees are not hurt by the cicada egg-laying even though the die-back of twigs may look significant. (Photo 4) Small trees and shrubs may be impacted by the flagging. Valuable plants near emergence areas can be protected with netting, if practical. Otherwise the sensible option is to tolerate the damage. Insecticide sprays are not an efficient option for most people, though orchards and nurseries can protect susceptible plants with frequent sprays.
It’s been a great summer for watching and listening to the periodical cicadas. I hope you got out to see and hear them. And I hope you logged all observations and reports on www.magicicada.org. Seventeen years from now those observations will be useful!
Female periodical cicada inserting eggs into a stem with her ovipositor.
Periodical cicada eggs within stem. Note the double row of eggs.
Egg-laying scars on aronia stem created by periodical cicada female laying eggs into the stem.
"Flagging" or dead twigs caused by periodical cicada egg laying.