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Disease Note.

Occurrence of Fusarium subglutinans on Cymbidium Orchids in New Zealand. P. G. Broadhurst, New Zealand Institute for Crop & Food Research Ltd, Mt Albert Research Centre, Private Bag 92169, Auckland, New Zealand . W. F. T. Hartill, c/o Mt Albert Research Centre, Private Bag 92169, Auckland, New Zealand. Plant Dis. 80:711. Accepted for publication 10 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0711D.

Orchid plants (Cymbidium sp.) showing dark brown to black, irregular, necrotic lesions on leaves were received from several commercial orchid greenhouses in the northern half of the North Island of New Zealand during 1990 to 1995. On some plants, a slimy rot of entire shoots was associated with advancing lesions at the base of leaves, and brown lesions were also seen on pseudobulbs. Symptoms were observed on several Cymbidium cultivars including Tracy Reddaway Geyserland, which appeared (o be particularly susceptible to the disease. Pieces of infected plant tissue were sampled, surface sterilized, and plated onto dishes containing potato dextrose agar. Fusarium subglutinans (Wollenweb. & Reinking) P. E. Nelson, T. A. Toussoun, & Marasas (syn. Fusarium moniliforme J. Sheld, var. subglutinans Wollenweb. & Reinking) was regularly isolated from necrotic leaf, shoot, and pseudobulb tissues, and F. moniliforme J. Sheld, occasionally isolated from necrotic leaf lesions. Koch's postulates were completed after inoculating wounded leaves and pseudobulbs of Cymbidium with a spore suspension of F. subglutinans. In New Zealand, F. subglutinans has previously been reported associated with a seedling blight, stalk rot, and ear rot of maize (Zea mays L). Snyder and Hansen combined the species in section Lesiola as used by Wol-lenweber and Reinking to form F. moniliforme J. Sheld. emend. W. C. Snyder & H. N. Hans. (3). The causal agent of a slimy soft rot of 1-year-old Cymbidium seedlings was identified by W. C. Snyder as F. moniliforme (2). In more recent years, F. subglutinans has been reported as the causal agent of a fungal disease in commercial cultivations of Cymbidium in Italy (1).

References: (1) G. D'Agliano and C. Carrai. Inf. Fitopatol. 44(6):24, 1994. (2) I. O. Gleason el al. Bull. Am. Orchid Soc. 35:294, 1966. (3) W. C. Snyder and H. N. Hansen. Am. J. Bot. 32:657, 1945.