Zonate Leaf Spot of Kenaf Caused by Cristulariella moricola.. P. D. Colyer, Louisiana Agricultural Experiment Station, Red River Research Station, Bossier City 71113. P. R. Vernon, and W. D. Caldwell. Louisiana Agricultural Experiment Station, Red River Research Station, Bossier City 71113. Plant Dis. 76:861. Accepted for publication 16 March 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0861A.
In recent years there has been an interest in growing hoaf (Hibiscus cannabinus L.) in Louisiana as an alternative crop. The plant is used to produce packing material, oil absorbents, animal bedding, and pulp for paper. In September 1991, following a prolonged period of wet weather, a severe leaf spot and blight of foliage was observed on kenaf in test plots on the Red River Research Station. Symptoms progressed from small, circular, tan lesions with dark brown margins to large lesions with concentric rings, appearing as target or zonate leaf spots. The spots eventually encompassed the entire leaf, causing a blight. Blighted leaves fell to the ground. Microscopic examination of blighted leaves showed the conical conidia of the causal agent, Cristulariella moricola (Hino) Redhead. Koch's postulates were completed by inoculating leaves of plants with agar disks containing mycelia of the fungus. The disease has been observed previously on kenaf in Maryland (2) and North Carolina (1), but this is the first reported observation in Louisiana. References: (1) L. F. Grand. Plant Dis. Rep. 62,841. 1978. (2) F. G. Pollack and H. E. Walerworlh. Plant Dis. Rep. 53:810, 1969.