Why Does Phlebiopsis gigantea not Always Inhibit Root and Butt Rot in Conifers

This review aims to identify possible causes of differing effectiveness of artificial biological control of Heterobasidion root rot by the saprotrophic fungus Phlebiopsis gigantea. We describe published information in terms of pathogen–competitor relationships and the impact of environmental and genetic factors. We also revisit data from original research performed in recent years at the Forest Research Institute in Poland. We hypothesized that, in many cases, competition in roots and stumps of coniferous trees between the necrotrophic Heterobasidion spp. and the introduced saprotroph, Phlebiopsis gigantea, is affected by growth characteristics and enzymatic activity of the fungi, the characteristics of the wood, and environmental conditions. We concluded that both wood traits and fungal enzymatic activity during wood decay in roots and stumps, and the richness of the fungal biota, may limit biological control of root rot. In addition, we identify the need for research on new formulations and isolates of the fungal competitor, Phlebiopsis gigantea, as well as on approaches for accurately identifying the infectious threat from pathogens.