Distribution and dynamics of mycophagous and microbivorous nematodes in potato fields and their relationship to some food sources

Summary Nematodes are not uniformly distributed in soil. The aim of this study was to investigate the distribution pattern of mycophagous and microbivorous nematodes and to develop sampling methods to detect them at different sites in the soil. Sampling of nematodes was carried out by three methods: using an auger, by collecting soil which was shaken from the roots (root shaking sample) and by collecting roots with the adhering rhizosphere soil (rhizosphere sample). Distribution patterns and population dynamics of mycophagous nematodes were similar to other microbivorous nematodes in three potato fields. Population densities in the rhizosphere samples were 4–50 times higher than those in auger samples. Samples obtained with the auger and root‐shaking methods yielded more or less equal population densities. Numbers of the mycophagous nematodes Aphelenchus avenae, Aphelenchoides sp. and unidentified microbivorous nematodes increased several fold within a few days on suitable substrates in soil. These substrates could be the dying roots of plants of which the haulms were killed or flax straws that were previously colonised by the fungus Rhizoctonia solani.