Cicadas Leave Trail of Dead Leaves
By Matthew Palmer
As you travel through our region, you may notice stands of trees with branch tips covered in dead leaves. The damage is not from the hot and humid weather, but rather the aftermath of the cicadas.
The days of hearing their mating calls and watching them flying and climbing on every surface have passed but the cicadas are still with us. The adults that made the big show are gone – consumed by predators, while alive, or scavengers and decomposers in death. But the eggs they laid remain in the treetops.
Each brown branch tip you see is a spot where a female cicada sawed through a small twig with an appendage on her abdomen and laid a group of eggs. When those eggs hatch – six to ten weeks after being laid – the newborn nymphs will drop to the ground, burrow down into the soil, and begin feeding on tree roots.
After 17 years, they will emerge as adults and the cycle will start anew. Though it may look like the trees with dead branches are dying in the midst of a summer heat wave, few will actually die from the damage. The dead branches will soon fall as the living buds behind the damaged areas begin to grow. Though the damage to branches and tree roots can slow a tree’s growth, that will be offset by fertilization from all those dead cicadas (and the waste from the animals that ate them).
They are now quiet, small, and will spend most of their lives below ground, but the cicadas are still with us. You probably just won’t hear about them again in this region until Brood X emerges in 2021.
Palmer is a forest ecologist in the department of Ecology, Evolution, and Environmental Biology at Columbia University.