How does the emerald ash borer affect ash trees?

Adult female emerald ash borers (Agrilus planipennis) lay eggs on the bark of ash trees during late spring and summer. Once the larvae hatch, they bore into the tree and feed on the phloem and outer sapwood layers, creating S-shaped tunnels that disrupt the tree’s vascular system. This disruption girdles and eventually kills the tree. Infested trees may exhibit a thinning leaf canopy, splitting bark, and increased woodpecker activity. In North America, fewer than 1 in 1,000 trees survive an infestation.