In October 1997, severe leaf spotting was observed on several ornamental plants growing in different nurseries in southern Italy. These symptoms were detected for the first time on strawberry tree (Arbutus unedo L.) and water wattle (Acacia retinodes Schltdl.). In the latter species, diseased plants showed also stem canker and shoot blight symptoms. Cylindrocladium pauciramosum C.L. Schoch & Crous (teleomorph Calonectria pauciramosa) were found associated with these symptoms (2). More recently, leaf spots were found also on feijoa (Feijoa sellowiana Berg.) and on Florida hopbush (Dodonaea viscosa (L.) Jacq.) in two other nurseries located in Sicily. Infected tissues were surface-sterilized and plated on potato dextrose agar. Plates were incubated at room temperature under fluorescent cool white lights on a 12-h light/dark regime. A Cylindrocladium species was consistently associated with diseased tissues. The isolates of Cylindrocladium collected from feijoa and Florida hopbush were identified on carnation leaf agar as C. pauciramosum on the basis of their obpyriform to broadly ellipsoidal terminal vesicles, conidiophore branching pattern, and conidium morphology, as well as mating type studies with tester strains of C. pauciramosum (1,3). Koch's postulates were fulfilled by inoculating 6-month-old seedlings of the four ornamental plants with a spore suspension of the fungus (104 conidia per ml). Following inoculation, all plants were maintained in a glasshouse where the temperature was 15 to 25° C and relative humidity was 80 to 90%. After 6 to 8 days, symptoms resembling those seen in the nurseries were apparent. The Cylindrocladium species was reisolated from lesions on inoculated plants, thus confirming it to be the causal organism of these diseases. This is apparently the first report of C. pauciramosum leaf spot on these hosts.
References: (1) P. W. Crous and M. J. Wingfield. Mycotaxon 51: 341, 1994. (2) G. Polizzi and P.W. Crous. Eur. J. Plant Pathol. 105:407, 1999. (3) C. L. Schoch et al. Mycologia 91:286, 1999.