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For the past half century, the latent period and the infectious period introduced by Vanderplank have dominated any discussion of plant disease epidemics. In Vanderplank’s model the reproduction curve is given by a square temporal flush of progeny production between time p and time p + i. Alternatively, the first two temporal moments of the reproduction curve provide a pair of reproductive time scales: the mean delay time between infection and progeny production and the standard deviation about this mean. For the simple case described above, in which every infection follows exactly the same reproductive time course, the values of the moments are uniquely determined by the values of p and i. In reality, there is considerable variability in these time scales among individual infections because of several factors including: somatic differences in host tissue, differences in microclimate within the plant canopy, as well as the inherent range of virulence within the pathogen population. For such a dynamic situation the meaning and use of latent and infectious period are shown to be ambivalent and their use can be misleading.<p><p>Keywords: NA