This guide is intended to assist field personnel in identifying life stages of, and damage caused by, emerald ash borer (EAB) (Agrilus planipennis Fairmaire). This difficult-to-detect insect causes symptoms in ash trees similar to those caused by many other abiotic and biotic causes. When diagnosing ash tree problems, it is important to step back and look at the whole picture as many diagnostic clues can be obtained by analyzing site conditions. Symptoms in EAB infested trees initially occur in the top portion of the canopy for the first 1-3 years after infestation.