Displaying items by tag: brood x

Here is some evidence of tree browning and “flagging” caused by the recent appearance of Brood-10 cicadas earlier this summer.  Courtesy Oak Ridge National Laboratory 

Tree “flagging” is a lingering sign of the 17-year cicadas’ brief time on Earth

(Alexandra DeMarco is an intern in ORNL’s media relations group.)

On the road leading to the U.S. Department of Energy’s Oak Ridge National Laboratory, drivers may notice that many of the green trees lining the entrance to the lab are dappled with brown leaves. At first glance, the sight isn’t extraordinary, as deciduous tree leaves turn hues of oranges and browns before falling to the ground each autumn.

Yet, just weeks past the summer solstice, this phenomenon is out of place and is in fact evidence of another natural occurrence: cicada “flagging.”

This spring, Brood X cicadas emerged from the ground after 17 years and swarmed across the eastern United States, leaving a trail of exoskeletons and echoes of mating calls. Cicadas emerge in such large quantities to withstand predation and successfully maintain their populations, and trees actually play a key role in their life cycle.

A male cicada attracts a female through a mating call, the sound responsible for cicadas’ shrill hum. After the two mate, the female cicada uses a sharp tubular organ called an ovipositor to slit the bark and split the sapwood of young tree branches to deposit her eggs there. These incisions, however, damage a tree’s vascular system and can cause stalks beyond the incision to die and wither, leaving behind twigs with brown leaves that resemble flags dangling from the trees.

The eggs then grow into nymphs that make their way to below ground. An oft-repeated misconception is that they’ll stay dormant for 17 years. Actually, during that time, they go through 5 life stages while feeding on the xylem (tree sap) of roots. This may further weaken saplings that were heavily infested with cicadas.

Eva Millwood holds Brood X cicadas on her property in South Knoxville in this submitted photo.

We will see a groundswell of East Tennessee 17-year cicadas as the heat comes on.

We have been hearing about it for weeks, online and on TV and in print. After 17 years underground, millions of cicadas are going to climb out of their burrows, shed their juvenile skins, unfurl their wings and fly up into the trees for one last grand jester of panache and reproduction and death. You even read about Brood X cicadas in Hellbender Press.

The Tennessee Wildlife Resources Agency posted a recent Instagram photo of a wild turkey jake with a crop stuffed full of cicadas, and there are reports of cicadas emerging en masse in parts of Tennessee. But your local searching self may ask: Where are they?

Insects are largely ectothermic. That means their body temperature comes from the surrounding air, water or ground temperature. The periodical cicadas need a ground temperature of roughly 68 degrees, eight inches deep to become very active. And we really have not had that for a sustained length of time.

Last week seemed to be destined to be the first big week of the emergence of Brood X. Monday started strong but the weather turned unusually cool for early May with daytime highs in the low 60s. Some of the cicadas started to ease out but it was primarily dozens, not hundreds or thousands, and certainly not 1.5 million per occupied acre. And remember, they are not everywhere.