White Grubs Under Apple Tree Bark: Wood Borers Require Pruning, Not Panic

Half-inch white grubs and powdery frass under bark on Macoun and Gravenstein apple trees (but not Yellow Transparent) indicate wood-boring beetles. Most borers in fruit trees are not fatal; the tree can compartmentalize damage.

Action: Prune out affected limbs in late winter before sap flow. Apples tolerate heavy pruning well. Contact the local Cooperative Extension office for species-specific advice, as borer complexes vary by region. No insecticide needed if pruning is thorough.