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Shoot Blight and Stem Dieback of Pieris japonica Caused by Phytophthora citricola, P. citrophthora and Botryosphaeria dothidea. W. W. P. Gerlach, University Fellow, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster 44691, and The Ohio State University, Columbus 43210; H. A. J. Hoitink(2), and C. W. Ellett(3). (2)(3)Associate Professor, and Professor, respectively, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster 44691, and The Ohio State University, Columbus 43210. Phytopathology 64:1368-1370. Accepted for publication 14 May 1974. DOI: 10.1094/Phyto-64-1368.

Dieback of Pieris japonica in Ohio nurseries can be caused by Phytophthora citricola, P. citrophthora, and Botryosphaeria dothidea. The Phytophthora spp. cause leaf and twig blight on young tissues and olivaceous leafspots on leaves of intermediate maturity that turn necrotic brown and are surrounded by a dark-red margin. Infected leaves commonly abscise, but lesions rarely progress into mature wood. Uninjured mature leaves and stems are resistant. Both of these Phytophthora spp., as well as P. cinnamomi, cause root and crown rot, which is characterized by stunting and chlorosis followed by leaf epinasty, dieback, and eventual death of plants. In landscape plantings and nurseries Botryosphaeria dothidea causes dieback on injured plants or plants under stress. Defoliation is followed by dieback of mature twigs and branches and the entire plant may be killed. Pestalotia sydowiana and a Phomopsis spp. may be involved as secondary invaders in the dieback complex.