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A Model of Damping-off and Root Rot of Douglas-Fir Seedlings Caused by Fusarium oxysporum. W. J. Bloomberg, Forest pathologist, Canadian Forestry Service, Environment Canada, Victoria, B.C.; Phytopathology 69:74-81. Accepted for publication 11 July 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-74.

The mathematical relationships required to construct a model of damping-off and root rot of Douglas-fir seedlings caused by Fusarium oxysporum were derived from the literature, unpublished data, and experiments. A time and space frame of 180 days from sowing, in plots 0.1–0.2 m² × 20 cm deep containing up to 100 seedlings, was selected. Simplifications and assumptions in the model included use of temperature as the main environmental factor, subdivision of time into 5-day periods and space into 2-cm intervals, with one vertical and one horizontal dimension, and natural variation based on pseudo-random selections from normal distributions. Using chi-squared goodness-of-fit, model predictions of germination, root growth and root rot mortality were not significantly different from nursery results in 4 yr. Predictions of number of seedlings and seedling roots infected ranged from 72 to 120% of nursery results.