According to the Virginia Cooperative Extension Service, 17-year cicadas will start to emerge from the ground around May 1st and damage many species of ornamental and hardwood trees. Oaks are commonly attacked, but the most seriously damaged plants are newly-planted fruit and ornamental trees such as apple, dogwood, peach, hickory, cherry, and pear. Pines and other conifers are not commonly attacked, and sometimes non-woody plants will have adult cicadas on them.
Newly-planted trees can be covered with fine netting to protect the small tender twigs from egg-laying females. Secure the netting around the trunk to stop the cicadas from climbing up into the tree canopy. Remove the netting at the end of June when the adult periodical cicadas have died. Remove and destroy any flagged, damaged twigs where female cicadas have laid their eggs within 6 weeks, before the nymphs hatch and drop to the ground and get established on the roots of that tree.
For the full story, go to this VCES site.