Journal of Arboriculture 12(6): June 1986 155 A DESCRIPTION OF DECLINING AND BLIGHTED PIN OAKS IN EASTERN VIRGINIA by D. N. Appel and R. J. Stipes Abstract. Endothia gyrosa, the pin oak blight fungus, com- monly colonizes pruned branches and other wounds on pin oaks in Eastern Virginia communities. Sometimes the disease causes serious losses of valuable shade trees. In one out- break of pin oak blight, diseased trees had a greater rate of decline in increment growth over a 25 yr. period than healthy, uninfected trees. As a result of this growth decline and the remedial pruning needed to remove dead and injured branches, blighted trees had smaller heights and diameters than healthy, uninfected trees. No single environmental factor, i.e., nutrients, precipitation, or root disturbance caused by the installation of underground utilities, was responsible for the oc- currence of pin oak blight. Endothia gyrosa has been found causing cankers on a wide variety of hosts including various oak (Quercus spp.) (9, 12, 13, 14, 15), chestnut (Castanea spp.) (11), sweet gum (Li- quidambar spp.) (10), beech [Fagus spp.) (9) and holly (Ilex opaca) (15). The range of this fungus in the United States extends from Ohio south to South Carolina, and westward through Mississippi into Texas. Pruning wounds or other, naturally oc- curring wounds on trees are reported to be impor- tant infection courts for the fungus (5, 10, 12, 15). Also, E. gyrosa has been described as a facultative parasite that infects trees weakened by environmental stress (5, 11). We present additional experimental evidence to support the involvement of drought in pin oak caused by E. gyrosa on Q. palustris. The coloniza- tion of artificially inoculated, pruned branches on pin oaks in field plots was found to be greatest during July and August, the hotter and sometimes driest months of the year in the research area (5). Cankers caused by E. gyrosa on inoculated, con- tainerized pin oaks elongated only when trees were exposed to water stress (1). Regularly watered trees were not significantly colonized by the fungus. Pin oak blight in Tidewater, Virginia is described as the most damaging of those diseases caused by E. gyrosa (1, 12, 14). The problem is par- ticularly serious because pin oak is an important component of the urban forests of eastern Virginia communities. The fungus causes girdling cankers leading to premature defoliation, dieback, and general decline of trees. Severely girdled, dying trees are often found adjacent to unaffected, healthy trees. Remedial pruning and fertilization are routinely used by homeowners to control the disease, but there is no evidence these measures are effective. A site was selected for study of pin oak blight at Langley Air Force Base (LAFB) near Hampton, VA, where large numbers of trees were infected by E. gyrosa. The objective of the study was to measure disease severity, and to classify site and tree characteristics to aid in determining factors responsible for the increasing incidence and severity of pin oak blight in the Tidewater region. This report discusses results from that study. Materials and Methods The pin oak population in the Langley communi- ty was systematically surveyed and inventoried in stages. In the first stage, 179 pin oaks located on nine residential streets were surveyed in 1977. Data collected during the survey included tree heights, diameters at breast height (dbh = 4.5 ft), and vigor assessment based on a 1-10 scale, where 10 represented a disease-free tree and 1 represented a dead tree. This subjective health rating consisted of assessing crown loss to disease and subsequent pruning. Also, the amount of dead limbs and branches in the crown, leaf color, and presence of suspected pathogens were considered in rating the trees. In 1978 and 1979, the survey was expanded in a second stage to include all 566 pin oaks in the communi- ty. Increment cores were removed from 33 selected trees in 1979. Cores were taken at 4.5 ft above ground, and measured by the Tree Growth Analysis Service, Department of Plant Pathology, Physiology and Weed Science, VPI &