Severe dieback on black oak trees on New York's Long Island was first apparent in the late 1980s. A twig- galling cynipid wasp and a fungal canker were associated with crown dieback. Symptoms were more severe in residential and urban park "ecotypes" than forested areas. Residual gall wasp populations from within twigs were compared among ecotypes and three crown categories (low, moderate and severe dieback). Insect populations were significantly greater on trees with severe crown dieback in residential areas and urban parks. In forested areas, insect numbers were similar among crown...