Urban green spaces as emerging hotspots for Phytophthora diversity: a global synthesis of host associations, distribution and management gaps

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Urban green spaces are increasingly recognised as interfaces for plant health, yet their role in shaping the diversity and spread of Phytophthora remains poorly synthesised globally. We compiled 166 records of Phytophthora –host associations from 16 peer-reviewed studies (2005–2025) across botanical gardens, parks, street trees, and managed urban landscapes. Only confirmed pathogenic interactions were included. The dataset comprised 28 Phytophthora taxa and 96 host taxa from 11 countries, yielding 133 unique associations. Diversity was highly uneven, with a few taxa dominating urban systems. Phytophthora multivora was the most frequently recorded taxon and had the broadest host range, followed by P. nicotianae , P . cinnamomi and P . ramorum . Associations were concentrated in angiosperms, especially Ericales, Myrtales, and Fagales, with Ericaceae, Myrtaceae, and Theaceae prominent. Nearly 60% of hosts were non-native, reflecting ornamental horticulture and global plant trade. Records were geographically biased, with Spain and South Africa accounting for over two-thirds of observations, while many regions remain underrepresented. A median 6-year lag between sampling and publication may delay recognition of emerging risks. Urban environments support structured Phytophthora communities shaped by host composition, environment, and human-mediated plant movement, functioning as reservoirs and sources of inoculum for surrounding ecosystems. To address management limitations, we propose a conceptual framework that integrates prevention, detection, response, and recovery into an adaptive cycle for urban green spaces, supporting pathway-based biosecurity, risk prioritisation, and coordinated surveillance. Our study highlights the need for more balanced global surveillance and coordinated management of Phytophthora in urban and peri-urban landscapes to improve urgently needed resilience and biosecurity outcomes globally.

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