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Dispersion and Deposition of Spores of Fomes Annosus and Fluorescent Particles. R. L. Edmonds, Assistant Professor (Research), College of Forest Resources, University of Washington, Seattle 98195; C. H. Driver, Professor of Forest Pathology, College of Forest Resources, University of Washington, Seattle 98195. Phytopathology 64:1313-1321. Accepted for publication 14 March 1974. DOI: 10.1094/Phyto-64-1313.

Fomes annosus, spread by airborne spores is an important pathogen in intensively managed conifer forests. This study examined dispersion and deposition patterns of conidia and fluorescent particles in relation to meteorological conditions. Experiments were conducted on 60 × 60 m sampling grids in a cleared area, at the edge of a 20-m-high Douglas-fir forest, and in the forest. Particles and spores were trapped with Rotorod samplers at heights of 1, 5, 10, 15, and 20 m. Deposition of fluorescent particles was determined on petri plates set 30 cm above the forest floor, simulating major infection courts. Wind speed and direction and temp were measured. Fluorescent particles generally dispersed in a similar manner to conidia. Horizontal and vertical dispersion was greater at night in the forest than in the cleared area, but this was reversed during the day. Dispersion was also affected by vegetation density with plumes being moved around areas of high density. Deposition in the forest was lower at night and higher during the day than deposition in the cleared area. At the forest edge at night, deposition was heavy due to local turbulence. Airborne concns were predicted with a dispersion model within a factor of two of observed, but deposition patterns were not reliably predicted. Natural spore deposition rates ranged from 0.0003 to 0.007 spores per cm2 per h with the maximum occurring at night on a sampler close to the forest edge.

Additional keywords: epidemiology.