This dataset scores the relative risks of Phytophthora x alni infection for 50034 fragments in Scotland identified as containing any of the three alder species susceptible to the pathogen (common alder, Italian alder and grey alder). Fragment risk scores integrate climate suitability (using pathogen-specific temperature-dependent growth curves and a relative humidity threshold), proximity to rivers/flooding, connectivity to other alder fragments via flood events and recent planting of alder under forestry grant schemes. Data and models used to score risk factors are variable in their time frames, but are broadly representative of the period from 2013 to 2023. Phytophthora disease of alder has been widespread in southern England since at least 1995 and became more prevalent in annual surveys between 1994 and 2003. It has been confirmed at several riparian sites in Scotland. P. x alni diseases are reported only from the alder genus. Full details about this dataset can be found at https://doi.org/10.5285/824f9ba8-7d1c-4a82-b5ec-a4f850f1d370
