Newswise — By the time billions of periodic cicadas announce their arrival in a chorus " some might say cacophony " of sound, the bugs may have already exerted their greatest impact on the trees that serve as their hosts, suggests preliminary research at Indiana State University.
Known as Brood X " or Brood 10, lest anyone get the idea the X stands for anything particularly ominous " the winged insects emerging over the next few days have been living underground for 17 years, sapping nutrients from the roots of trees. Brood X is the largest of several broods of 17-year cicadas.
As any parent will tell you, food consumption by humans tends to increase during the teen years and the same is apparently true of cicadas.
A study of red maple trees in Shakamak State Park in conjunction with 13-year cicadas that emerged in 1989 and 2002 found the greatest impact on tree growth occurred just prior to emergence, said James Speer, an assistant professor of geography who specializes in dendrochonology, the study of tree rings to analyze environmental events. "Over the last five years before the emergence, the ring widths were getting smaller and smaller. Then the year of emergence, the trees were actually released, they grew faster," Speer said. "Then when the cicadas go back into the ground as young nymphs, there seems to be suppression again for a number of years." The Shakamak findings surprised scientists, who had expected the greatest impact would come during the time of the insects' emergence when female cicadas cut small slits in tree branches in which to lay their eggs. The impact on certain other tree species, including red oak, was less severe. Studies of additional tree species in other locations are needed before scientists can draw any conclusions, Speer said. Speer and Keith Clay, a biology professor at Indiana University, have obtained a $400,000 National Science Foundation grant to study the affect of cicadas on the forest eco-system and whether cicadas reduce the growth of some trees while other trees grow faster. "It can affect the succession or the stage of species dominance in the forest," Speer said. Still, Speer and other scientists do not recommend taking any action to mitigate the effects of the cicadas' emergence. "It is a natural part of the system. Cicadas have been around much longer than we have so it's not something that we need to control," he said.
While it might be possible to reduce the impact by placing nets over tree canopies to prevent female cicadas from laying their eggs in tree branches, Speer said such procedures would be time consuming and costly and might only be worth consideration by orchard owners or others whose livelihoods may depend on trees.
Sure their sound can be annoying and their numbers so great it may be hard to walk without stepping on a cicada, but experts say the insects pose no threat to humans or their pets, which may actually prefer eating cicadas instead of their favorite pet food. The cicadas will remain active above ground for only a few weeks so by mid-July their presence in more than a dozen Midwestern, Eastern and Southern states will be just a memory until they emerge again in 2021.While they're around, it will make for a "cool" experience, said Josh Frizzell, a Lowell, Ind. resident who will graduate from Indiana State in August with a bachelor's degree in geology "It's not even something that a lot of people are aware of," Frizzell said. "I spoke to some high school students that came in for a science symposium about a month back and that was one of the things that they were most interested in. It's kind of interesting you have an insect outbreak. It's something you don't see every day. It's something that the public's interested in too and it's something that's cool to kind of put the word out."
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