Environment & Conservation

Brood X and The Knifelike Ovipositors

Cool band name, right? Brood X is indeed musical, and their infrequent performances are loud and memorable. They are 17 year periodic cicadas. They are due to emerge any day now.

During the last cicada summer, 17 years ago, I was a student of Computer Science, and I subleased an apartment in Bloomington while I worked a local internship and took summer classes at Indiana University. The campus there is natural and semi-wooded, and when the cicadas emerged, they did so in force. I didn’t have a garden at that time, but I didn’t notice any obvious damage to the plant life on campus. For the most part, all I noticed was the deafening sound they produced. I had to wear ear plugs to go outside, because my ears physically ached from the collective volume of cicada mating songs.

Now I find myself in another natural, wooded setting. And this time, I’m responsible for the care of a young orchard. I’ve tried to read and prepare as much as possible for the upcoming cicada emergence, and I hope I have done well enough. I have learned that cicadas are native insects, that they play an important role in our ecosystem, that they’re fascinating and unique, and that they should be revered and protected rather than feared. I have read that the cicadas do not eat anything from the garden, nor do they feed on the foliage of trees or shrubs, nor do they harm humans, livestock, or pets. Insecticide sprays are neither needed nor effective against them.

Cicadas do, however, lay their eggs in trees. To do this, they slice open pencil-width twigs with their saw-shaped ovipositors and lay their eggs inside. This shouldn’t cause any long term problems for established trees, where all the pencil-width twigs are located near the extremities of the tree. But it could spell big trouble for young trees like mine where the main trunk falls within the cicada’s preferred size range. The official recommendation to prevent damage is to wrap the whole tree lollipop-style to keep the cicadas out. But with nearly a thousand trees to wrap, the amount of fabric I would need to accomplish this could break my annual budget.

Young trees wrapped for cicada protection

Instead, I am attempting a compromise. I cut long strips of floating row cover fabric, about 3″ wide. I am wrapping multiple layers of these fabric strips around the main trunks and any branches that are within 3/8″-7/8″, the cicada’s preferred size range. Maybe the cicadas will be able to slice through the fabric and do their damage anyway, but I think it’ll be difficult for them. Row cover fabric is stretchy and a little clingy, and I can’t slice through it very easily with my pocket knife. I think it’s likely that the serrated ovipositors will get stuck in these fabric layers, and that they’ll quickly become frustrated and move on to a bigger tree. There’s a whole forest nearby, after all.

I think it unlikely that many cicadas will emerge in the field where the young trees are planted. Since that field had no trees last time the cicadas emerged, it’s unlikely that any eggs were laid there. Perhaps some cicadas will travel from the woods to the field of young trees, or maybe I’ll get lucky and they’ll all stay in the woods. I’ll be monitoring the situation closely and taking copious notes so I can be prepared the next time they return, 17 years from now.

For more information:
“Emergence of the 17-Year Cicada” by Purdue University
“Brood X is almost here. Billions of cicadas to emerge in eastern US” by CNN