Cicadas are a very interesting insect in the world of entomology. Several different broods have been identified and named with roman numerals. They emerge on a 13 or 17 year schedule with good predictability. Some exceptions, or “stragglers,” will emerge every year. We do not have a good prediction for the annual cicada emergence as they tend to be quite erratic.
The emergence of millions of cicadas in a relatively short time frame provides a striking visual image and the sounds they produce can be deafening. The males produce the sounds by using specialized structures on the abdomen. They fly to high, sunlit branches and sing together in choruses in an effort to attract females. Each species has a distinctive sound.
After mating, the females lay their eggs in ¼ to ½ inch diameter twigs. They prefer oak, hickory, apple, peach, or pear trees. Six to ten weeks later the eggs hatch and fall to the ground. The tiny nymphs burrow into the soil in search of tree roots to feed on the sap. Some damage to trees from the subterranean nymphs does occur but otherwise healthy trees typically can tolerate the damage.
Cicada brood XIX (13 year brood) is expected to emerge this year in Western Kentucky. Mature nymphs begin to emerge when the soil temperatures reach 64 degrees F; usually late April or early May. The nymphs will dig up the soil surface, similar to crayfish, and crawl up vertical structures such as trees or houses to molt into the adult stage. It typically takes about 3+ weeks for the majority of cicadas to fully emerge and molt. Some areas in Western Kentucky will likely see more cicadas than other areas so rest easy if you don’t see as many as your neighbor across the county.
Periodical cicadas are potential pests of many trees and other woody ornamentals. Physical injury or “flagging” occurs after females slit twigs to insert eggs. Often, the end of the twig or branch will die and fall off and the eggs hatch and burrow into the ground in preparation for the next emergence 13 or 17 years later. If practical, cicada nymphs can be pruned out. This needs to be done within a three week window, after egg laying has ended. Although a time-consuming process, it may be a viable alternative to protect the long term value of backyard fruit trees.
To combat damage, recommendations include postponing new tree plantings until after cicada’s have laid their eggs. Young trees can be covered with netting to protect tender twigs. Make sure to secure the netting around the trunk as cicadas will climb up the trunk under the net. Some sprays are available for commercial orchards but require several applications during the season; often two times per week for good deterrence. Insecticides are not recommended for homeowners.
If you have questions about cicadas or protecting your trees, give us a call at the Henderson County Extension Office; we are happy to help!
