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Disease Note. Leaf Spot of Cherry Laurel in Spain Caused by Pseudomonas syringae pv. morsprunorum. E. Mateo- Sagasta, Departamento de Patología Vegetal, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040-Madrid and Centro de Investigaciones Biológicas, CSIC, Velázquez, 144, 28006-Madrid. R. Beltrá, Departamento de Patología Vegetal, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040-Madrid and Centro de Investigaciones Biológicas, CSIC, Velázquez, 144, 28006-Madrid. Plant Dis. 74:615. Accepted for publication 2 February 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0615C. A leaf spot disease of cherry laurel (Prunus laurocerasus L.) was
characterized by necrotic lesions surrounded by a dark halo. The necrotic
tissues often dropped out, leaving a "shot-hole" appearance.
This disease was found in a nursery near Pontevedra and was suspected
to be of bacterial origin. Nearly pure cultures of a fluorescent bacterium
were isolated from lear spot using 523 medium and King's medium B.
Based on results of LOPAT and other tests, the pathogen was keyed
to a pathovar of Pseudomonas syringae van Hall. Gelatin was not
hydrolyzed, and neither were casein, aesculin, and arbutin; tyrosinase
was produced and acid was produced in purple lactose agar; and
white growth developed in 5% sucrose broth (1). The bacterium was
identified as P. s. pv. morsprunorum (Wormald) Young et ai, an organism
not previously found in Spain. Nursery-grown laurel plants
spray-inoculated with 7 X 107 cfu/ml developed typical leaf spot within
15-20 days. The pathogen was reisolated from the lesions. |