The genus Phytophthora includes plant pathogens that threaten agriculture, horticulture, urban forests, and conservation efforts in natural ecosystems. While over 200 species are globally described, only 91 have been reported in Australia, emphasising a significant biosecurity risk from overseas incursions. Urban forests, including botanic gardens, are increasingly recognized as reservoirs of Phytophthora diversity, serving as "bridgeheads" for pathogen introduction into natural ecosystems. Botanic gardens, with their diverse exotic plant collections, can act as sentinel plantings for early detection of new Phytophthora incursions in Australia.

In response to tree establishment failures linked to Phytophthora, the Botanic Gardens of Sydney launched the "Stop the Rot Project" (STRP). A survey of tree nursery stock (2021–2023) revealed a 22% positive rate for Phytophthora and identified concerning species diversity, including the first Australian reports of P. mediterranea (a biosecurity threat). A concurrent survey at the Blue Mountains Botanic Garden reported P. plurivora on Rhododendron for the first time in Australia. This species has subsequently been associated with dieback of the endangered Dwarf Mountain Pine (Pherosphaera fitzgeraldii) within the Greater Blue Mountains World Heritage Area. This highlights the critical need for biosecurity monitoring in botanic gardens to provide sentinel information and prevent the introduction of Phytophthora into natural ecosystems.

STRP efforts are now focused on developing an innovative and cost-effective batch leachate system for Phytophthora detection in plants, soil, and water with a focus on nurseries, national parks and botanic gardens. These findings will inform strategies to mitigate the spread and impact of Phytophthora.