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Development of Gray Leaf Spot on Sorghum in Burkina Faso. Melville D. Thomas, Principal Sorghum Pathologist, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), B. P. 910, Bobo Dioulasso, Burkina Faso, West Africa. Plant Dis. 75:45-47. Accepted for publication 1 June 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0045.

The development of gray leaf spot on sorghum, caused by Cercospora sorghi, was monitored between 1986 and 1988 for a total period of 5 wk each year. The top four leaves of tagged plants infected by natural inoculum were rated weekly for disease severity on a 16 scale. Symptoms of gray leaf spot first appeared either shortly before or several days after anthesis. Thereafter, the progress of the disease was slow and symptoms became more severe toward physiological maturity. Final disease severity ratings on the fifth week in 1986 were 3.3, 3.6, and 3.9 for the sorghum lines ICSV 1001 BF, ICSV 16-3 BF, and ICSV 20-1 BF, respectively. In the following years, disease ratings on the fifth week were 4.8, 5.6, and 6.0 in 1987 and 2.4, 3.6, and 5.5 in 1988 for ICSV 1001 BF, ICSV 16-3 BF, and IS 18696, respectively. Area under the disease progress curve was largest for ICSV 1001 BF in 1986 and for IS 18696 in 1987 and 1988. The late appearance of gray leaf spot in West Africa implies that the disease may have little effect on yield.