Incidence of Sugarcane Smut in Louisiana and Its Effect on Yield. J. W. Hoy, Assistant Professor, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station. C. A. Hollier, Assistant Specialist, and D. B. Fontenot, Assistant Specialist, Cooperative Extension Service; and L. B. Grelen, Research Associate, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Center, Louisiana State University, Baton Rouge 70803. Plant Dis. 70:59-60. Accepted for publication 24 June 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-59.

Sugarcane (interspecific hybrids of Saccharum) infected by Ustilago scitaminea was observed in 13 of 15 sugarcane-growing parishes in 1984. Frequency of observed infested fields and incidence of diseased plants within fields were highest in susceptible cultivars CP 73-351 and NCo 310, intermediate in moderately susceptible cultivars CP 65-357 and CP 74-383, lowest in resistant cultivars CP 70-330 and CP 72-370, and absent in CP 70-321 and CP 72-356. Cane tonnage yields were negatively correlated (P = 0.01) with increasing levels of smut incidence observed in small plots in three plant-cane and one ratoon-cane field of CP 73-351. The most significant effect of smut on yield was a reduction in number of healthy stalks in diseased plots.