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Disease Note.

First Occurrence of Phytophthora cactorum Infecting Euonymus Cuttings. S. D. Barrie, Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, Ontario, Canada NOR 1G0 . W. R. Jarvis, Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, Ontario, Canada NOR 1G0. Plant Dis. 80:822. Accepted for publication 14 May 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0822D.

Cuttings of Euonymus japonica Thunb, from a nursery in southwestern Ontario displayed symptoms of a dark brown discoloration spreading along the stem above the soil line. Root formation was inhibited and leaves on the stem senesced and fell off. The inside of the stem exhibited a dry brown rot, mostly confined to the pith. Isolations from the edge of the discolored area yielded a diffuse, hyaline mycelium on potato dextrose agar (PDA) that produced lemon-shaped sporangia in sterile distilled water characteristic of Phytophthora. To confirm Koch's postulates, macerated cultures grown on PDA at 25C were mixed with sterile perlite into which fresh cuttings were placed. After incubation for 2 weeks in the greenhouse at about 25C, the cuttings exhibited a brown discoloration spreading up the stem, and the leaves on the stem senesced and fell off. Cutting open the stem revealed a dark brown dry rot confined to the pith. Isolations taken from these cuttings yielded the same Phytophthora species. All isolates were identified as P. cactorum (Lebert & Cohn) J. Schrot. by D. J. S. Barr of the National Identification Service, Centre for Land and Biological Resources Research in Ottawa, Ontario, Canada. This disease appears to differ from a basipetal withering caused by a Phytophthora sp. closely related to P. citrophthora (R. E. Sm. & E. H. Sm.) Leonian, reported in California (1). This is the first recorded occurrence of P. cactorum infecting E. japonica

Reference: (1) R. Keimet al. Calif. Agric. 35(5/6): 16, 1981.