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Ecology and Epidemiology

Modeling Control Strategies for Laminated Root Rot in Managed Douglas-fir Stands: Model Development. W. J. Bloomberg, Research scientist, Pacific Forestry Centre, Canadian Forestry Service, 506 West Burnside Road, Victoria, B.C. V8Z 1M5; Phytopathology 78:403-409. Accepted for publication 22 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-403.

A model of laminated root rot caused by Phellinus weirii was developed to assess potential control strategies in managed Douglas-fir stands. The model mimicked key processes in disease initiation and development quantified as functions of time and space. These processes were horizontal and vertical tree root distribution, root contact with inoculum and among root systems, spread of mycelium through root systems, root decay, reduction of diameter growth in infected trees, tree mortality, and persistence of inoculum in roots of stumps and killed trees. The processes were expressed as mathematical functions which were integrated in a computer program to calculate spread of the disease and stand-growth loss and mortality. Data for quantification of functions were obtained by experiments and from the literature. Simulated control practices included infected stump removal, sanitation fellings, and mixed planting of Douglas-fir and resistant species. Accuracy of the model was tested by comparing calculated disease spread and mortality with the following data: 1) spread and damage in two 60-yr-old, 1-ha stands in Oregon, 2) results from a statistically based model for spread and damage that has performed satisfactorily, and 3) observed spread and damage behavior in stands of different ages and growth rates. Results from the model compared favorably with all of the above situations.