Periodical cicada years are actually quite beneficial to the ecology of the region. Cicada egg-laying in trees serves as a natural “pruning” that results in increased fruit yields in the succeeding years. And emerging cicadas turn over large amounts of soil, and after they die, their decaying bodies contribute a massive amount of nitrogen to the soil.
Adult cicadas cause virtually no feeding damage. Due to their straw-like mouths they do not chew leaves of plants and cannot damage flowers.
The only damage cicadas cause to plants results from the egg-laying habits of females. Twigs with many slits made by the cicada’s ovipositor may break or hang down from the trees. On well-established trees this damage, called “flagging,” is not serious. Larger, mature trees often respond to this “pruning” of the ends of the branches by producing more branches. However, young or newly planted trees may be damaged if this type of injury is extensive. Some common trees that are susceptible to cicada damage include oak, maple, cherry and other fruit trees, hawthorn, and redbud. There are more than 270 different species of trees upon which that cicadas lay their eggs. Evergreens are rarely affected.
Control is not necessary on established trees. Insecticides are ineffective for significantly reducing cicada abundance and damage. Insecticides also pose a risk to people, beneficial insects, and birds. Consider delaying the planting of new trees or shrubs until fall when the cicadas are gone.
Small ornamental trees, shrubs, and fruit trees may be protected by covering them with plastic mesh (<0.5-inch openings) or cheesecloth. The plants should be protected from the time cicadas emerge until they are gone 6-8 weeks later.
Ornamental ponds should be covered with screen or plastic mesh to prevent cicadas from accumulating. Large numbers of decomposing cicadas could cause problems with oxygen depletion in the water. Clean pool skimmers/filters frequently during cicada emergence to keep them from getting clogged.
Cicadas pose no health threat to people or pets. They cannot bite or sting and if they land on you, it is purely accidental. They do not carry any diseases communicable to humans.
In general, it does not hurt cats or dogs to eat cicadas. However, veterinarians have reported cases in which pets have consumed so many cicadas simultaneously that the non-digestible skins had blocked portions of the pets’ digestive tract.