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Disease Detection and Losses

Modeling the Influences of Plant Infection Rate and Temperature on Potato Foliage and Yield Losses Caused by Verticillium dahliae. K. B. Johnson, Former research associate and lecturer, Department of Plant Pathology, University of Minnesota, St. Paul 55108, Present address: Dept. of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Phytopathology 78:1198-1205. Accepted for publication 15 April 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1198.

A simple submodel was coupled to a dynamic potato growth simulation model to quantitatively describe the effects of Verticillium dahliae infection on loss of crop leaf area and tuber yield. This was accomplished by accelerating the leaf tissue aging rate as a function of V. dahliae incidence in stems and high-temperature stress. A Gompertz equation was used to describe the temporal incidence of V. dahliae in potato stems, and the effects of temperature were described by a linear deviation of the daily mean above 17 C. Values for the modelís parameters were determined from sequential, within-season harvests of crop biomass and V. dahliae incidence data from five inoculated crops of Russet Burbank potato grown in three seasons. Among experiments, modeled final tuber yield, area under the tuber dry matter accumulation curve, and area under the leaf area index curve were correlated with the observed values. In two crops with similar infection rates, modeled and observed yield loss was 4.6 and 6.5%, respectively, when conditions were relatively cool (mean temperature = 20.0 C) and 17 and 15%, respectively, when conditions were warmer (mean temperature = 23.3 C). In simulation analyses, the model indicated that mean air temperature after infection, the proportion of individual stems infected by V. dahliae, and timing of infection are important considerations for interpreting yield losses caused by this pathogen.

Additional keywords: crop growth modeling, potato early dying, Verticillium wilt.