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Cicada Damage Photo

Image 1. Cicada damage is typically restricted to the small, outer twigs. Trees may be completely covered by cicadas or have a few isolated dead twigs. All trees in these images are expected to suffer no serious long term effects from this damage. Images by Clifford Sadof of Purdue University and Pennsylvania Department of Conservation and Natural Resources – Forestry.

Purdue Landscape Report: Dead leaves covering trees (image 1) or on the ground beneath them (image 2) in July would normally be a worrying sign for tree health, but this year much of the damage can be blamed on 17-year cicadas. This damage is unlikely to cause serious trouble for healthy, large trees and management is relatively simple. The choice to prune or not to prune comes down to cost, aesthetics, and concern for the next generation of cicadas.

How Cicadas Damage Plants

Cicada damage is similar to a light pruning and should not be an issue for healthy, mature trees. Cicadas damage trees when they lay their eggs in small twigs (3/16 to 1/2 inch in diameter) on deciduous trees and shrubs. They have a long, thin body part called an ovipositor that resembles a sewing needle that they stab into plants to lay their eggs. This action creates small holes and cracks in the bark (image 3). If enough cicadas lay their eggs in a twig, it can damage the bark enough to kill the twig (image 1).

Cicada Damage Leaves on Ground Photo

Image 2. The dead twigs killed by cicada egg laying may break off the tree and litter the ground underneath. Image by Pennsylvania Department of Conservation and Natural Resources – Forestry.

Recognizing Cicada Damage
The degree of cicada damage depends on insect density and the number of trees in the area. To determine if a tree or bush has been damaged by cicadas, ask the following questions:

Cicada Scars Photo

Image 3. Cicada egg laying damage varies between tree species, but is consistently in a straight, length-wise line along the branch. Note that all four examples also have signs of either puncture marks, cracks in the bark, or some combination of the two. Images by John Ghent, Clifford Sadof of Purdue University, Tim Tigner of Virginia Department of Forestry, and Pennsylvania Department of Conservation and Natural Resources – Forestry.

1.  Were there 17-year cicadas within 50 meters (~164 ft) of the tree this year? Cicadas do not travel very far. If there weren’t noticeable numbers of 17-year cicadas nearby the damage was likely caused by something else.
2.  Is the damage on a deciduous tree or bush? Cicadas rarely lay their eggs on evergreen trees and herbaceous plants. Damage on these types of plants is likely caused by something other than the cicadas.
3.  What size of branches and twigs are damaged? Cicadas show a strong preference for small twigs (3/16 to 1/2 inch in diameter). As a result, damaged trees may appear as though their outer layer of leaves is dead while the inner leaves remain healthy (image 2). If larger branches are dead, the damage was probably not caused by cicadas.
4.  Does the bark have typical egg laying damage? If you can reach the damaged twigs, look for a row of puncture wounds often connected by cracks length-wise along the branch. Their appearance may vary between tree species (image 3), but they will almost always be length-wise.

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Resources:
Billions of Cicadas Are Coming This Spring; What Does That Mean for Wildlife?, Got Nature? Blog, Purdue Extension-Forestry and Natural Resources (FNR)
17 Ways to Make the Most of the 17-year Cicada Emergence, Purdue College of Agriculture
Ask an Expert: Cicada Emergence Video, Got Nature? Blog, Purdue Extension-FNR
Periodical Cicada in Indiana, The Education Store, Purdue Extension resource center
Cicada Killers, The Education Store
Cicada, Youth and Entomology, Purdue Extension
Purdue Cicada Tracker, Purdue Extension-Master Gardener Program
Purdue Landscape Report

Elizabeth Barnes, Exotic Forest Pest Educator
Purdue University Department of Entomology


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