Agrilus quercicola Fisher is a native buprestid associated with Gambel oak in Colorado. In recent years very high populations have developed in native stands, following host plant stresses that include sustained drought, above-average temperature and late frosts. This has resulted in outbreak populations that have crossed over into nurseries and have subsequently developed as landscape pests of oak in some areas along the Front Range of Colorado. A wide range of species of oak are susceptible and there has been serious damage to both nursery and landscape plants in 2003-2004. Data on life history, natural enemies and distribution will be presented.