Modelling the mechanisms behind the key epidemiological processes of the conifer pathogen Heterobasidion annosum

The Heterobasidion annosum species complex is a widely distributed group of fungal conifer pathogens causing root and butt rots. We studied the key processes of Heterobasidion epidemiology by compiling models that rely on biological processes. Models were included in the mechanistic model with stochastic elements, Hmodel, simulating the fungal dynamics in even-aged Norway spruce stands. The results from the modelling and stand-level simulations indicated that primary infections are affected by the stump size and spore deposition. In addition, we found that Heterobasidion dynamics at the scale of the stand are driven by several infections in large stumps, rather than by numerous infections in small stumps. We assessed the need for quantitative results in Heterobasidion biology, especially in the spread mechanisms, to support the development of complex mechanistic models.