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Bipolaris Leaf Blight of Panicum fasciculatum: Effects of Host Age and Photoperiod on Susceptibility. E. S. Luttrell, Professor, Department of Plant Pathology, University of Georgia, Athens 30602; H. B. Harris(2), and H. D. Wells(3). (2)Professor, Department of Agronomy, Georgia Experiment Station, Experiment 30212; (3)Plant Pathologist, USDA, Georgia Coastal Plain Experiment Station, Tifton 31794. Phytopathology 64:476-480. Accepted for publication 15 October 1973. DOI: 10.1094/Phyto-64-476.

Browntop millet, Panicum fasciculatum Swartz, is highly susceptible to leaf blight caused by Bipolaris (Helminthosporium) setariae (Saw.) Shoemaker in the early seedling stage and in the maturation stage. Resistance in young, as well as old, leaves increases from the seedling stage onward until plants 5-6 wk old are essentially immune. Resistance decreases sharply after plants begin to head at 6-7 wk, and blight is severe by the time seeds reach the hard dough stage at 8-9 wk. Vegetative growth and resistance may be prolonged indefinitely in plants grown under a 16-h light/8-h dark cycle. Hay is normally harvested before blight causes extensive damage. The disease appears too late to cause appreciable seed losses, and seedling infection in the field is not important, except as a bridge between seed-borne inoculum and mature plants.