Fomes

Abstract: Measurements of spore deposition in forests, obtained by exposing freshly cut sections of pine stem, indicate that in relatively calm conditions rates exceed 20 spores/100 cm.2/hr. close to sporophores. Deposition rates of 1–5 spores/hr. are commonly encountered in well-ventilated plantations where local spore sources occur. A simple method is described of trapping spores on muslin squares : they are later recovered by shaking with sterile water and plating the suspension on pine sections. By this means Fomes annosus and Peniophora gigantea were found to be regular components of the air spora in Britain. At selected places the rate of deposition on muslin squares was determined in winds of varied direction, and for both species rates of over 20 spores/100 cm.2/hr. were recorded close to forests. Rates declined with distance from source, but in the Shetland Islands, some 200 miles from source, the two fungi and other forest species were still detectable. Another method is given for determining the number of F. annosus spores on samples of conifer foliage. Examination of samples from some British forests shows that spores are widespread and vary greatly in abundance; there is some relation with proximity to sporophores. The limitations of this method for assessing the risk of stump infection in plantations are discussed.