Effects of sawdust amendment on forest soil fungal community and infestation by cockchafers

Effects of Scots pine wood amendment on the fungal community in forest soil infested with cockchafers and foraged or non-foraged by wild boars and hares were investigated. We hypothesized that sawdust amendment would increase the abundance of entomopathogenic and insect-associated species effective in cockchafer predation. The soil dilution method and morphotyping were used for fungal isolation and identification in order to quantify and qualify the viable components of the microbiota that are important for evaluating soil functions. There was usually increased abundance and decreased diversity of soil fungi one year after sawdust amendment. Application of pine sawdust more often increased than decreased the abundance of some insect-associated fungi or dermatophytes and keratinophilic species and decreased the number of cockchafer larvae. Abundance of Geomyces pannorum, Mortierella spp. + M. luteus, Pseudogymnoascus roseus, Tolypocladium inflatum and Trichoderma koningii increased, at least locally, whilst Chrysosporium merdarium, Penicillium spp. (including the most common P. citrinum, P. daleae and P. janczewskii), Sporothrix schenckii and Trichoderma spp. decreased. Application of pine sawdust under roots of 1-year-old Scots pine seedlings significantly increased the abundance of Phoma + Pyrenochaeta spp. in neighbouring soil, thus increasing the risk from Phoma blight. Trichoderma strigosum was among the dominants (frequency >5%). Another six and two Trichoderma species were among the subdominants (frequency 1–5%) and subrecedents (frequency <1%), respectively. Dermatophytes, coprophilous and keratinophilic species, e.g. Cephalotrichum, Chrysosporium merdarium or S. schenckii, occurred only or mostly in foraged plots. The altered communities resulting from pine sawdust amendment may contribute to biological control of the cockchafer larvae.