Wild Rice Yield Losses Associated with Growth-Stage-Specific Fungal Brown Spot Epidemics. C. L. Kohls, Former Research Assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55108. J. A. Percich, and C. M. Huot. Associate Professor, and Associate Scientist, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 71:419-422. Accepted for publication 20 November 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0419.

The effects of fungal brown spot (FBS), caused by Bipolaris oryzae, on the yield of wild rice (Zizania palustris) during various specific growth stages were studied for 2 yr. When epidemics of FBS were initiated at boot, heading, early grain elongation, and milk stages, reductions of 67, 56, 32, and 0% resulted compared with the nondiseased control. Disease curtailment treatments, consisting of applying inoculum at the boot stage and allowing the disease to progress to mid grain elongation, milk, and grain ripening, resulted in yield reductions of 39, 74, and 74%, respectively, compared with the nondiseased control. A critical-point yield loss model derived from multiple linear regression analysis of disease severity data on the three uppermost leaves at the milk stage accounted for 87% of the variation in yield in the disease onset treatments.

Keyword(s): Cochliobolus mayabeanus.