Oregon ash grows along the streams and wetlands of western Oregon and Northern California, where it provides important wildlife habitat. But these trees are threatened by the emerald ash borer, an insect pest that has spread from Europe and the eastern U.S. Because ash trees often suffer damage from common pests and diseases, emerald ash borer infestation can be hard to distinguish. This guide focuses on damage from insect pests such as the Oregon ash bark beetle, foliage diseases like leaf spot, or even issues like drought and heat. Here's what you need to know to rule out emerald ash borer.
