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Disease Note.

First Report of Zonate Leaf Spot on Silverbell Tree Caused by Cristu-lariella moricola. G. E. Holcomb, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural; Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. Plant Dis. 78:1217. Accepted for publication 30 August 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1217D.

Silverbell (Halesia diptera J. Ellis) is a small, native flowering tree that occurs from South Carolina to eastern Texas and is propagated and grown as an ornamental. Partial defoliation of 500 silverbell trees was observed in a Louisiana nursery in October 1993. Individual leaves exhibited round, tan, zonate leaf spots that were up to 8 mm in diameter. The pathogen was identified as Cristulariella moricola (Hino) Redhead based on the distinctive shape of conidia produced in leaf spots. The fungus was readily isolated from leaf spots when placed on 2% water agar and was maintained on potato-dextrose agar. Conidia used for the pathogenicity tests were produced on V8 juice agar. Pathogenicity of the fungus was determined by mist-inoculating detached silverbell leaves with a suspension of 780 conidia per milliliter and incubating them in a moist chamber at about 25 C. Leaf spots similar to those originally observed appeared within 24 hr, and C. moricola was reisolated from infected leaves. H. diptera and the family Styracaceae represent a new host and host family for C. moricola (1,2).

References: (1) L. F. Grand. Plant Dis. Rep. 62:841, 1978. (2) J. C. Trolinger et al. Plant Dis. Rep. 62:710, 1978.