The value of sentinel plants for risk assessment and surveillance to support New Zealand’s biosecurity

Better surveillance for early detection of invasive alien species in natural ecosystems, or on valued plants found in modified areas, could prevent the potentially devastating and costly impacts (whether environmental, economic or cultural) of new invasions on the affected country. However, within a country, geographic location and spatial scale put constraints on what surveillance and eradication tools can be deployed effectively. Therefore, determining which species represent a significant pest risk before they reach the border is considered an effective strategy. Surveillance of expatriate sentinel plants provides an important component for biosecurity efforts with the aims of i) identifying insect pests, nematodes and plant diseases attacking expatriate native species, and ii) developing pest risk analysis profiles to eliminate or mitigate the risk of arrival. Biosecurity is an important focus in New Zealand because it is an isolated island nation with high rates of endemism and an export-focussed economy dominated by primary products from agriculture, horticulture and forestry. This review examines some of the challenges and opportunities provided by sentinel plant research, including designing a program to ensure it is fit for purpose with clear scientific aims, as well as selection of sentinel plant species, taxa of interest, geographic location of sentinels and invaders, detection, frequency of monitoring and sampling methods. Current examples of sentinel plant research include projects using existing networks of botanical gardens and arboreta that demonstrate the importance of coordination through the International Plant Sentinel Network (IPSN). These examples complement ongoing research using managed planting of selected sentinel plant species in selected countries. The value of these approaches to inform plant biosecurity efforts in New Zealand are considered as well as potential areas for future research.