Will the cicadas harm plants? If they do, what can I do to protect my flowers, trees, and bushes?

Cicadas do not harm anything except trees, and they do very little damage to them. The adult cicadas that are starting to emerge do not eat anything. The females will do slight damage to young tree branches when they cut a slit in the bark and lay their eggs. The branches will sometimes die, but not do any lasting damage to the trees. The eggs hatch and drop to the ground where the cicadas will spend the next seventeen years as nymphs feeding on the roots of trees, but not doing anything that will kill the tree.White Teeth