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Disease Detection and Losses

A Critical-Point Yield Loss Model for Cylindrocladium Black Rot of Peanut. J. K. Pataky, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650, Present address: Department of Plant Pathology, University of Illinois, Urbana 61801; M. K. Beute(2), J. C. Wynne(3), and G. A. Carlson(4). (2)Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650; (3)Associate professor, Department of Crop Science, North Carolina State University, Raleigh 27650; (4)Professor, Department of Economics, North Carolina State University, Raleigh 27650. Phytopathology 73:1559-1563. Accepted for publication 8 June 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1559.

Three approaches were used to estimate peanut yield loss due to Cylindrocladium black rot for two commercial cultivars and two advanced-generation breeding lines which were evaluated in 10 field trials in four North Carolina counties in 1980, 1981, and 1982. Results from trials in stratified fields and established plots, and from Cylindrocladium black rot simulations, were similar for a highly susceptible commercial cultivar (Florigiant), a moderately resistant commercial cultivar (NC 8C), and a highly resistant breeding line (NC 18229). A critical-point model for predicting incidence of Cylindrocladium black rot approximately 1 wk before digging explained disease incidence-yield relationships when yield was expressed as the percentage of the maximum yield at a location. Critical-point models for Florigiant, NC 8C, and NC 18229 were: Y=98.8 - 72.7 X (r2 = 0.84); Y = 100.2- 74.5 X (r2 = 0.79); and Y = 98.3 - 66.6 X (r2 = 0.57), respectively, in which Y = predicted percentage maximum yield and X = incidence at the critical rating date. In trials where epidemics developed naturally, mean incidence 1 wk before digging ranged from 0.21 to 0.74, 0.17 to 0.53, and 0.13 to 0.33 and mean predicted yield loss ranged from 15 to 53%, 13 to 40%, and 9 to 22% for Florigiant, NC 8C, and NC 18229, respectively. A single critical-point model was not applicable over locations for NC 18016, which appeared to be less agronomically stable than the other lines evaluated in this study.

Additional keywords: Arachis hypogaea, Cylindrocladium crotalariae, disease loss assessment, epidemiology.