The radio said our 17 yr Cicada onslaught would cause little damage. WRONG! They lay eggs under the bark of new growth. The eggs supposedly hatch and the grubs fall and burrow into the ground. The spits damaged a lot of my young oaks and fruit tree growth. Now the supposed grubs are in the soil. Are they now feeding on my roots? Should I apply a grub killing granual or spray to the soil?