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The Relation Between Total, Infectious, and Postinfectious Diseased Plant Tissue. M. J. Jeger, Department of Plant Pathology, East Malling Research Station, Maidstone, Kent ME19 6BJ, England; Phytopathology 72:1185-1189. Accepted for publication 19 November 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1185.

A new mathematical analysis that links the rates of change of total, infectious, and removed (postinfectious) diseased plant tissue is presented. Equations are obtained that give the proportion of total diseased tissue that is infectious or postinfectious in terms of biologically meaningful parameters. These are the rate of increase per infectious diseased tissue, and the rates at which disease progresses from the latent to the infectious and from the infectious to the postinfectious condition. Comparisons with the parameters R, p, and i of Vanderplank’s differential-difference equation are made. Reported instances in which disease increase is unexpectedly rapid after a fungicide program ends are explicable in terms of this analysis, but experimental corroboration is lacking.

Additional keywords: theoretical epidemiology.