In: Bevers, Michael; Barrett, Tara M., comps. 2005. Systems Analysis in Forest Resources: Proceedings of the 2003 Symposium. General Technical Report PNW-GTR-656. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 1 M. Thor is a program leader at Skogforsk, Uppsala Science Park, S-751 83 Uppsala, Sweden; T. Möykkynen is a researcher at the Faculty of Forestry, University of Joensuu, Finland; J.E. Pratt is a forestry officer (emeritus) at the Northern Research Station, Scotland; T. Pukkala is a professor at the Faculty of Forestry, University of Joensuu, Finland, J. Rönnberg is a researcher at the Southern Swedish Forest Research Centre, Alnarp, Sweden; C.G. Shaw III is a national program leader for pathology research, USDA Forest Service, Washington D.C. USA; J. Stenlid is a professor at the Swedish University of Agricultural Sciences, Dept. Forest Mycology and Pathology, Uppsala, Sweden; G. Ståhl is a professor at Swedish University of Agricultural Sciences, Dept. Forest Resource Management and Geomatics, Umeå, Sweden; S. Woodward is Head of Discipline Agriculture & Forestry, School of Biological Sciences, Univerity of Aberdeen, Scotland. Systems Analysis in Forest Resources: Proceedings of the 2003 Symposium MODELING INFECTION AND SPREAD OF HETEROBASIDION ANNOSUM IN CONIFEROUS FORESTS IN EUROPE M. Thor, T. Möykkynen, J.E. Pratt, T. Pukkala, J. Rönnberg, C.G. Shaw III, J. Stenlid, G. Ståhl and S. Woodward 1 INTRODUCTION The pathogenic fungus Heterobasidion annosum (Fr.) Bref. causes severe problems for forestry throughout the northern temperate zone, infecting mainly coniferous trees. Annual losses in the European Union are estimated at €790 million. In Sweden annual revenue losses attributed to decay and impacts on growth reach approximately €60 mil- lion. Apart from affecting income for the forest owner, H. annosum impacts the industry: pulp and paper manufactur- ers and sawmills experience log quality problems because of the fungus. The extent of decay is difficult to estimate in standing trees; even so, some deduction for the risk of decay gener- ABSTRACT The pathogenic fungus Heterobasidion annosum causes severe problems for forestry throughout the northern temperate zone, infecting mainly coniferous trees. Annual losses in the European Union are estimated at €790 million. The infection biology of the fungus is well described, although variation is considerable. This paper describes two modeling projects in Europe. The first, MOHIEF (Modeling of Heterobasidion infection in European forests), is a project within the European Union aiming to produce a decision-support tool for forest managers, as well as a tool for scientists throughout Europe. MOHIEF models infection and spread of the pathogen for various tree species over a range of forest conditions. The other project, Heureka, aims to produce a system for forest planning on strategic, tactical and operative levels in Sweden. Although national in scope, the model can be applied at regional and local levels. In Heureka the impact of H. annosum is one factor amongst other components that include growth and yield, wood properties, biodiversity, biomass-carbon relationships and forest-owner behavior. In this paper simulations of infection by Heterobasidion are demonstrated together with examples of how the models can be exploited, from a forest manager’s and a scientist’s perspective. 105 ally is built into stumpage prices. The likelihood of infec- tion can be minimized by active means such as selection of the right season for cutting, stump treatment, or stump removal. These measures have a cost, however, and thus must be integrated into forest planning to fit the “right” operations to the “right” stands. THE PATHOGEN H. annosum forms perennial fruiting bodies that pro- duce vast numbers of spores under suitable environmental conditions. In Sweden, spore dispersal takes place during the whole growing season (April to September) with a peak