Sentinel trees for early detection of non-native forest pests and pathogens in Australia

Analysis of non-native forest pest and pathogen establishments for Australia over the past 30 years has revealed most new arrivals are detected through observations on urban trees, supporting efforts to enhance sentinel tree surveillance in urban landscapes. Here we describe sentinel tree surveillance programs in Australia and highlight opportunities that will improve our efforts for early detection of non-native pests and pathogens that threaten forest plantations, amenity landscapes and the natural environment, including both specific (targeted) surveillance and general surveillance (e.g., public engagement). Australia’s urban landscapes are composed of a mix of indigenous (e.g., Corymbia, Eucalyptus, Lophostemon ) and non-indigenous (e.g., Pinus, Platanus, Ulmus ) genera. Use of these urban trees as sentinels for early detection of non-native forest pests and pathogens commenced more than 25 years ago, with surveys of elm trees ( Ulmus ) for Dutch elm disease in Melbourne in 1998. State-based programs targeting sentinel trees around high-risk sites (e.g., ports of entry, cargo distribution centres) for early-detection of a broad range of forestry pests and pathogens began in Melbourne, Sydney, and Brisbane over a decade ago. This has now been expanded into a national program co-funded by industry and State governments, Forest Watch Australia, with sentinel tree surveillance implemented across most capital cities in Australia. Engagement with the public, local councils and arborists is used to enhance general surveillance capability in urban landscapes, with training workshops on detection and reporting, and development of a mobile phone based application to facilitate field recognition and reporting to government agencies for action. The network of Australia’s botanic gardens has played a key role in these initiatives, particularly those capital city gardens with high visitation from overseas tourists. Botanic gardens have had a strong role in outward facing public engagement programs as well as being host to workshops and national sentinel tree programs, including linkages with the International Plant Sentinel Network co-ordinated by Botanic Gardens Conservation International. Here we also describe recent research efforts to incorporate remote sensing and artificial intelligence to enhance sentinel tree surveillance and the use of molecular tools to enable more rapid and accurate diagnostics (e.g., high throughput sequencing). Opportunities to improve sentinel tree surveillance are discussed.