The increasing threat to European forests from the invasive foliar pine pathogen, Lecanosticta acicola

European forests are threatened by increasing numbers of invasive pests and pathogens. Over the past century, <i>Lecanosticta acicola,</i> a foliar pathogen predominantly of <i>Pinus</i> spp., has expanded its range globally, and is increasing in impact. <i>Lecanosticta acicola</i> causes brown spot needle blight, resulting in premature defoliation, reduced growth, and mortality in some hosts. Originating from southern regions of North American, it devastated forests in the USA's southern states in the early twentieth century, and in 1942 was discovered in Spain. Derived from Euphresco project 'Brownspotrisk,' this study aimed to establish the current distribution of <i>Lecanosticta</i> species, and assess the risks of <i>L. acicola</i> to European forests. Pathogen reports from the literature, and new/ unpublished survey data were combined into an open-access geo-database (http://www.portalofforestpathology.com), and used to visualise the pathogen's range, infer its climatic tolerance, and update its host range. <i>Lecanosticta</i> species have now been recorded in 44 countries, mostly in the northern hemisphere. The type species, <i>L. acicola</i>, has increased its range in recent years, and is present in 24 out of the 26 European countries where data were available. Other species of <i>Lecanosticta</i> are largely restricted to Mexico and Central America, and recently Colombia. The geo-database records demonstrate that <i>L. acicola</i> tolerates a wide range of climates across the northern hemisphere, and indicate its potential to colonise <i>Pinus</i> spp. forests across large swathes of the Europe. Preliminary analyses suggest <i>L. acicola</i> could affect 62% of global <i>Pinus</i> species area by the end of this century, under climate change predictions. Although its host range appears slightly narrower than the similar <i>Dothistroma</i> species, <i>Lecanosticta</i> species were recorded on 70 host taxa, mostly <i>Pinus</i> spp., but including, <i>Cedrus</i> and <i>Picea</i> spp. Twenty-three, including species of critical ecological, environmental and economic significance in Europe, are highly susceptible to <i>L. acicola</i>, suffering heavy defoliation and sometimes mortality. Variation in apparent susceptibility between reports could reflect variation between regions in the hosts' genetic make-up, but could also reflect the significant variation in <i>L. acicola</i> populations and lineages found across Europe. This study served to highlight significant gaps in our understanding of the pathogen's behaviour. <i>Lecanosticta acicola</i> has recently been downgraded from an A1 quarantine pest to a regulated non quarantine pathogen, and is now widely distributed across Europe. With a need to consider disease management, this study also explored global BSNB strategies, and used Case Studies to summarise the tactics employed to date in Europe.