2018 cicada brood may not appear in Pennsylvania, experts say
Cicadas are nothing if not punctual, but even their predicted arrival after 17 years is not always a sure thing.
Last exposed to the legendary underground insects in 2016, Western Pennsylvanians should prepare themselves for more emergences in 2018 and 2019, experts say.
If the 2018 emergence materializes, it will be limited to Allegheny, Butler and Washington counties and western Westmoreland County, said Linda Hyatt, Penn State Extension assistant.
“Sometimes it just happens in pockets,” she said.
Over the course of eight years, Pennsylvania can be exposed to eight different populations, known as broods, of cicadas. The broods emerge from underground after a 17-year maturation process, according to the Penn State Department of Entomology.
Immature nymphs usually emerge in May or June, sometimes in the millions, shed their skins and mate. Males are known for their loud mating calls, which can create an eerie soundtrack for the early weeks of summer.
After the mating ritual, females deposit hundreds of eggs in the twigs of trees. Adults have a short lifespan of three to four weeks above ground. Once the eggs hatch, the young nymphs drop to the ground and enter the soil, where they stay another 17 years, according to Penn State.
Although Penn State is predicting a 2018 emergence in four counties, the population, known as Brood VII, is small and getting smaller. Some experts, online and otherwise, dispute that the song of the cicadas will be heard at all next year in Western Pennsylvania.
“Unless there's something I haven't heard, I don't think we're going to see them here,” said Bob Davidson, invertebrate zoology collection manager at the Carnegie Museum of Natural History in Pittsburgh.
Davidson said Brood VII, because of predation by birds and other factors, may be “dwindling down to extinction.” The next big emergence in Western Pennsylvania — Brood VIII — is scheduled for 2019, although outliers could manifest themselves in 2018, he said.
Brood X, a widespread, multistate emergence expected in 2021, also could see a lot of advance emergences, he said.
“In some cases, even when a brood is expected to emerge, an area may or may not see them. If it's in an area where there's been rapid development, that can affect the population numbers,” said Chuck Gill, spokesman for the Penn State College of Agricultural Sciences.
Brood VII in particular is threatened by climate change and land-use patterns, according to a 2004 study published in the Journal of the New York Entomological Society.
Although Brood VII emergences have been sighted in Western Pennsylvania, the population is mostly associated with the Finger Lakes region of New York. With the exception of American entomologist Charles Marlatt, who reported Brood VII emergences in Allegheny and Washington counties, most sources limit Brood VII to New York.
A 1968 article in the Transactions of the American Entomological Society concluded that the Pennsylvania sightings of Brood VII may actually have been outliers associated with Brood VIII.
The 2004 study also makes no mention of Pennsylvania and posits that the New York population is under threat.
“Periodical cicada Brood VII has declined significantly in the past century, since 27 of 37 previously recorded locations were devoid of cicadas in 2001,” the study said. “Thus, all available evidence suggests that Brood VII has become extinct in many previously reported localities. This extinction, occurring within the span of only a few generations, indicates that, even given their typically large population sizes, these animals may be vulnerable to rapid decline.”
The study said farming, development practices and climate change may be to blame, but more research is needed.
Whether the cicadas appear next in 2018 or 2019, the Pennsylvania Farm Bureau wants fruit growers and grape growers to take the necessary precautions. Cicadas can damage young fruit trees and young grape vines (2 years or younger) by inserting their eggs into branches and vines, said spokesman Mark O'Neill.
“Vineyard owners or grape growers can use circular netting in an effort to protect vines from cicadas,” he said, “while fruit growers may consider not planting new trees in a year when they anticipate a large emergence of cicadas.”
Stephen Huba is a Tribune-Review staff writer. Reach him at 724-850-1280, firstname.lastname@example.org or via Twitter @shuba_trib.