VIEW ARTICLE

Ecology and Epidemiology

Production of Sori and Dispersal of Teliospores of Ustilago scitaminea in Louisiana. J. W. Hoy, Associate professor, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803; M. P. Grisham(2), and C. P. Chao(3). (2)Research scientist, Sugarcane Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Houma, LA 70361; (3)Former graduate assistant, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803, Present address: Taiwan Banana Research Institute, P.O. Box 18, Chiuju, Pingtung 90403, Republic of China. Phytopathology 81:574-579. Accepted for publication 17 January 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-574.

Production of sori by Ustilago scitaminea was monitored during two growing seasons in smut-inoculated sugarcane clones in Louisiana. The production of sori began during May, increased sharply during June, and continued at a lower rate through October. Smaller peaks in sorus production occurred in highly susceptible clones during August and October. Secondary infection cycles were detected in many highly and moderately susceptible clones and a few resistant clones. Sorus production began later and fewer sori were produced by resistant clones. Teliospore concentrations per cubic meter of air per day above the canopy increased with sorus production during June. Lower aerial spore concentrations during July and August were associated with increased precipitation. Aerial spore concentrations were reduced on average by 53 and 99% at distances of 15 and 135 m from the field. Mean spore concentrations increased during the afternoon and were highest from 5 to 7 p.m. Increasing spore concentrations were associated with increasing temperature and wind speed and decreasing relative humidity. The numbers of teliospores deposited on the soil within the crop were highest below and adjacent to sori, and then decreased rapidly with increasing distance.