Morus alba var. pendula (mulberry) is a favorite ornamental tree in Hungary. In 1998 and 1999, a canker disease was observed on this species in a western Hungarian ornamental tree nursery in Köszeg. Bark necrosis and cankers exposing the xylem were observed on the trunks of 1-, 2-, and 3-year-old trees. Pink sporodochia 200 to 400 μm in diameter were found in the necrotic bark. The fungus associated with the trunk cankers was identified as Fusarium lateritium Nees:Fr. f. sp. mori (Desmaz.) Matuo & K. Sato (1) from sporodochia and fungal isolates recovered from necrotic tissues. Isolations on potato dextrose agar yielded white colonies with a slight pink discoloration. Radial colony growth rate at 22°C and 12 h of light daily was 5 mm. Macroconidia were typical of F. lateritium, with three to eight septa. Microconidia were not observed. Intercalary chlamidospores (7 to 8 μm) rarely formed. Pathogenicity of the fungus was confirmed with a monoconidial culture. Three-year-old mulberry tree stems were inoculated with mycelial agar plugs. After 10 days, sunken necrotic lesions with a brownish discoloration, similar to naturally occurring cankers, developed. F. lateritium was successfully recovered from these lesions. No necrosis developed around control wounds. Mulberry Fusarium stem blight and canker is found in many temperate regions (2) but was not recorded as a disease of M. alba var. pendula in nurseries. This is the first record of the disease in Hungary.
References: (1) C. Booth. 1971. The Genus Fusarium. Commonwealth Mycological Institute, Kew, England. (2) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN.