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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of damping-off and root rot of Douglas-fir seedlings caused by Fusarium oxysporum were derived from the literature, unpublished data, and experiments.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 0.10.2 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.

Additional keywords: control, disease, simulation.