An Integrated Approach to Monitor and Control the Exotic Forest Pathogen Heterobasidion irregulare in Europe.

The North American fungal pathogen Heterobasidion irregulare is currently distributed in forest stands along 103 km of coastline west of Rome. This paper reviews and expands the knowledge on impacts, pathways of introduction and invasion, factors driving the invasion, and on the dispersal abilities of this pathogen in Italy. Further, an integrated disease management program to minimize the spread of the fungus in Europe is suggested, based both on published literature and on new findings reported here. Observational and genetic evidence support a single introduction through infected wood during WWII, and a subsequent invasion through spore dispersal. Experimental evidence suggests transmission potential of the pathogen rather than hyper-susceptibility of naive hosts is the major determinant of invasion. The current range of H. irregulare is too vast to suggest eradication, however we recommend minimizing the risk of spread of H. irregulare outside the zone of infestation while reducing the magnitude of infestations within its current range. We provide evidence suggesting the most cost-effective management approach hinges on preventing the saprobic establishment of the fungus in stumps in a “buffer” area surrounding the current zone of infestation.