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Sugarcane Leaf Scald Distribution, Symptomatology, and Effect on Yield in Louisiana. J. W. HOY, Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803. M. P. GRISHAM, USDA-ARS, U.S. Sugarcane Research Unit, Houma, LA 70361. Plant Dis. 78:1083-1087. Accepted for publication 31 August 1994. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994. DOI: 10.1094/PD-78-1083.

Sugarcane leaf scald, caused by Xanthomonas albilineans, was first observed in Louisiana in November 1992. During 1993, surveys were conducted to determine the geographic distribution of the disease and which cultivars were affected. Symptomatology was monitored in fields with diseased plants, and the effect on yield was studied. Leaf scald was detected in commercial fields of five of seven commercial cultivars. The number of fields of cultivars CP 70-321, CP 72-370, and LHo 83-153 affected and the incidence of plants within fields were low. A greater number of affected fields and higher disease incidence within fields were observed for cultivars CP 74-383 and LCP 82-89. The number of affected fields and the incidence of symptomatic plants were highest in areas located near the Gulf of Mexico, over which a severe hurricane passed during August 1992. Leaf scald was detected in numerous clones at the USDA-ARS research farm near Houma, Louisiana: and the disease was detected in yield trials and increase plots associated with the cultivar selection and release programs. Leaf scald was detected in both commercial and cultivar development plantings at a total of 46 sites in 12 of 18 parishes in which sugarcane is grown. Symptoms were present throughout the growing season. Leaf symptoms included bleaching; characteristic narrow, white pencil lines; and necrosis. Shoot and young stalk death and the development of symptomatic shoots from axillary buds of mature stalks also were observed. At one location, high disease incidence and drought stress in CP 74-383 resulted in extensive plant death and severe losses. Disease incidence, quantified as the number of symptomatic shoots or plants, was inversely correlated with yield in one of four fields. Stalk sucrose content was lower in symptomatic compared to asymptomatic stalks in all four fields; and juice purity, fiber content, and stalk weight were lower in three, two, and one field, respectively.