The PTR-MS technique was also applied to soils containing M. albus along with the plant pathogen Pythium ultimum and it was possible in situ to show the production of VOCs from M. albus. An estimation of the effective range of concentrations of total VOCs being produced by M. albus is in the order of 100–300 parts per billion (volume) based on the determination of the concentration of propanoic acid, 2-methyl methyl ester.