The first week of January 2022, Mother Nature delivered a one-two punch to tens of millions of people in the eastern half of the US as bone-chilling temperatures and heavy snow blanketed the region. Tens of thousands of homes and businesses were left powerless, sometimes for days, when trees toppled and branches broke, obliterating power lines and transmission cables below. During the aftermath of the storm, an interesting query cropped up in the media-sphere. Did rampant egg-laying by Brood X periodical cicadas last summer weaken tree branches that resulted in widespread power losses as limbs broke and tumbled onto power lines?
With abdomen pulsing, a female cicada inserts eggs into egg-nests sliced into twigs of a dogwood tree. If these small branches snap off in winter storms, are they heavy enough to bring down power lines?
Well, a cabal of cicada experts met last week to review the science behind the situation. In the first comprehensive review of periodical cicada biology, published in 1907, cicada expert C. L. Marlatt noted that “The part of the plant selected for a receptacle for the eggs is almost invariably the twigs of the previous year’s growth.” A later study by entomologists Fred Miller and Webster Crowley on more than 100 common shade trees reveled that periodical cicadas laid eggs in twigs ranging in size from ~4 mm to 11 mm (~ ⅛ to ½ inch) in diameter. Have a look at some of the images that accompany this narrative and you will see that the branches which turned brown or snapped and fell beneath trees as a result of cicada egg-laying, are small diameter twigs at most a few feet long. Even with a load of heavy snow it is highly unlikely that these small twigs would be heavy enough to break a transmission line.
Did periodical cicadas cause some injury to unprotected trees growing in orchards, shade tree nurseries, and landscapes? Surely cicadas cause some damage, but are they responsible for the widespread power outages associated with last week’s storms? Nah, this one belongs to Mother Nature having a bit of fun with our urban infrastructure.
Bug of the Week thanks utility companies in the DMV for providing the inspiration for this episode. We also thank Dan, Chris, and Paula for weighing in on the potential of cicada damage to down large limbs during snow storms. Two great references, “The Periodical Cicada” by C. L. Marlatt and “Effects of periodical cicada injury on woody plants” by Fredric Miller and Webster Crowley, were used to prepare this episode.