A brood of periodic cicadas not seen since 2003 is expected to emerge this year in parts of the United States. Farmers are being told to plan accordingly, as the insects pose a threat to fruit and ornamental crops.
Like clockwork, periodic cicadas from brood IX will be emerging across southwestern Virginia, parts of North Carolina, and West Virginia, according to a press release put out by Virginia Tech. Incredibly, 1.5 million cicadas are expected to emerge per acre in the affected areas.
Cicadas are easily recognisable, with their large bodies, big bulbous eyes, and transparent wings. They look a bit ominous, but they’re harmless to humans and pets. If you’re lucky, you might even find a discarded cicada husk on a tree branch.
Still, in their immature form, these bugs have spent the past 17 years underground, where they feed on the roots of trees. But the time has come for them to breed and renew the cycle in a task that will require immature cicadas, called nymphs, to leave their comfy subterranean confines, transform into an adult, and find a mate. And that’s where their iconic buzzing sound comes in, as the males attempt to woo a partner with their impressively loud high-pitched drones.
“Communities and farms with large numbers of cicadas emerging at once may have a substantial noise issue,” said Eric Day, an entomologist at Virginia Tech, in the press release. “Hopefully, any annoyance at the disturbance is tempered by just how infrequent — and amazing — this event is.”
Cicadas from brood IX last appeared in these parts in 2003, but some areas saw a cluster in 2013, as Brood II made their scheduled appearance. Periodic cicadas emerge in either 13- or 17-year intervals, but some cicadas, known as annual or dog-day cicadas, appear each year. Scientists aren’t sure why periodic cicadas have adopted these extraordinary rhythms, but it may be a way to avoid predators.
Periodic cicadas are among the longest-lived insects on Earth, though they spend the vast majority of their time as subterranean nymphs. When it’s time to leave the soil, the nymphs escape by building a tunnel through to the surface. Once on a tree branch or vine, the nymphs moult into their adult form.
“Cicadas can occur in overwhelming numbers and growers in predicted areas of activity should be watchful” said Doug Pfeiffer, a professor at Virginia Tech.
Cicadas don’t threaten crops by chewing on the foliage. Rather, they threaten the health of juvenile trees and vines because of the way they lay their eggs. Using a sharp tube called an ovipositor, a female cicada deposits her eggs within a branch or vine, causing it to split open and wither away in a process known as flagging. This can stunt the growth of trees and vines, or even kill the entire plant. Tree species at risk from cicadas include apple, dogwood, peach, hickory, cherry, and pear, according to Kent State.
Adult cicadas only live for around two to four weeks, and the entire emergence period of a brood doesn’t last longer than roughly six weeks. In terms of timing, the first periodic cicadas should start to appear in the affected areas in May, with a peak in early June. Most cicadas should be gone by July.
This mercifully short window means it’s manageable for farmers to mitigate the impacts of these bugs. Mitigation strategies include not planting trees or vines in the year or two leading up to an expected infestation, deploying netting, and spraying insecticides.
Enjoy them or curse them while you can, because these periodic cicadas will disappear again for another 17 years in one of the more bizarre circles of life.