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 25°C were mixed with sterile perlite into which fresh cuttings were placed. After incubation for 2 weeks in the greenhouse at about 25°C, 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. japonicaReference: (1) R. Keimet al. Calif. Agric. 35(5/6): 16, 1981.