Branch Dieback of Savin Juniper in Pennsylvania Caused by Diplodia mutila

Branch dieback of savin juniper (Juniperus sabina L.) was observed on a tree in Dauphin County, PA, in May 1996. The symptomatic tree was in an ornamental planting that had been established approximately 10 years previously. Branches were cankered and girdled, causing yellowing and death of foliage beyond the cankers. Black pycnidia occurred in necrotic bark of cankers. Dark, two-celled conidia obtained from these pycnidia produced pure cultures of Diplodia mutila (Fr.:Fr.) Mont., the anamorph of Botryosphaeria stevensii Shoemaker. The fungus was identified based on pycnidial, conidial, and cultural characteristics, and comparison with known isolates provided by N. A. Tisserat (2). Pathogenicity of a single conidial isolate from Pennsylvania was tested in a greenhouse by wounding and inoculating twigs of potted eastern red cedar (Juniperus virginiana L.) with water agar plugs colonized by mycelium. Cankers formed and enlarged to girdle and kill the inoculated shoots, from which the pathogen was reisolated. No symptoms developed on, nor was the pathogen isolated from, control twigs. B. stevensii has been reported more frequently on angiosperms, such as apple (Malus Mill.) and oak (Quercus L.), than on gymnosperms. However, a canker disease caused by B. stevensii previously has been reported to affect J. scopulorum Sarg. and J. virginiana in Kansas, Missouri, and Iowa (1,2). References: (1) P. H. Flynn and M. L. Gleason. Plant Dis. 77:210, 1993. (2) N. A. Tisserat et al. Plant Dis. 72:699, 1988.