Oak decline is a slow-acting disease complex that involves the interaction of biotic and abiotic factors such as climate, site quality and advancing tree age. Oak decline occurs more commonly among red oak species, but white oaks are susceptible as well. Oak decline can occur in forested and urban settings. Trees affected by oak decline show a reduction in growth, dieback, epicormic sprouting, yellowing leaves, sparse foliage and early leaf drop. Mature trees (>70 years) growing on dry sites with shallow or rocky soils on ridgetops are most affected. Once weakened with oak decline, trees are often more susceptible to secondary insects and pathogens (e.g. cankers) that can more easily defoliate or colonize a stressed tree. Management methods include those that promote tree health and vigor.