Safeguarding global plant health: the rise of sentinels

Abstract

The number of alien plant pests and pathogens is rapidly increasing in many countries as a result of increasing trade, particularly the trade in living plants. Sentinel plantings in exporting countries to detect arthropod pests and agents of diseases prior to introduction provide information about the likelihood of introduction and the potential impact on plants native to the importing country. Such plantings can consist of species that are native to exporting or importing countries ("in-patria" and "ex-patria" plantings). In-patria plantings consist of young woody plants of species that are commonly exported and can be used to identify pests that may be introduced to new countries via the trade in live plants. Ex-patria plantings consist of exotic young or mature woody plants and surveys may provide information about potential impacts of pests if these were to become established in a new country. We discuss the methods and benefits of this powerful tool and list examples of studies that highlight the large number of unknown organisms and pest-host relationships that can be detected. The usefulness of sentinel plantings is illustrated using examples of arthropod pests and fungal pathogens of European and Asian tree species that were identified in sentinel studies in China and the Asian Russia. Keywords Woody plants • Exotic pests and pathogens • Early warning Key message • Many exotic plant pests and pathogens are unknown prior to their establishment, making prevention and management difficult. • Sentinel plantings to detect pests and pathogens prior to introduction provide information about the likelihood of introduction and the potential impact on plants native to the importing country. • This paper discusses the different types of sentinel plantings based on the native range and age of the plants, their purpose, limitations and benefits. • Summarised results from published studies illustrate the benefits of sentinel plantings.

Biological Invasions in South Africa’s Urban Ecosystems: Patterns, Processes, Impacts, and Management

“…Such pests were therefore not on watch lists and could not have been regulated against. 'Sentinel plantings', that is, plants established outside their natural range, are increasingly being used to identify new host-pest associations, predict future tree health threats and fill gaps in pest risk analyses (Eschen et al 2018;Poland and Rassati 2018). The range of impacts caused by damaging invasive pests on tree health in South Africa are highlighted by the following case studies.…”

Fast and reliable molecular methods to detect fungal pathogens in woody plants

“…The trade in forest tree seeds is therefore considered to be high risk for the introduction of fungal pathogen in disease-free areas (Burgess and Wingfield 2002;Franić et al 2019), and sensitive tests are required to check their health status before movement (Ioos et al 2009a;Lamarche et al 2015). Sentinel planting, i.e., plants native to importing country planted in exporting countries that are inspected and analyzed at regular intervals for microbial pathogen detection, is the most promising tool (Eschen et al 2019). To this end, one could imagine associating other types of "biological" sensors that have already been the subject of promising studies, such as the sentinel plantations of European species exposed in an exotic environment (Vettraino et al 2015) or sentinel nurseries of non-native species found in their non-native environment of origin (Vettraino et al 2017).…”

Forewarned is forearmed: harmonized approaches for early detection of potentially invasive pests and pathogens in sentinel plantings

“…One of the earliest uses of sentinel species as an early warning system is from the early 20 th century when canary birds (Serinus canaria L.) were used in coal mines to warn of carbon monoxide hazards for workers. Sentinel plants in early warning systems are used too as indicators of potential risk associated with damage caused by pests or pathogens based on regular inspections of the plants for signs and symptoms of insect attack or disease (Wylie et al 2008;Paap et al 2017;Eschen et al 2018). For example, sentinel plants have been used to provide adequate warning for damage downy mildew on cucurbit crops, and roses planted at the end of vineyard rows can give an early warning for problems with powdery mildew.…”

“…Two main strategies apply to the sentinel planting concept: sentinel plantations and sentinel nurseries (Figs 1,2). A sentinel plantation ("ex-patria" plantings sensu Eschen et al 2018) can be defined as a plantation of non-native plants grown in an environment and monitored to identify biotic agents that affect the growth and vitality of those plants (Roques et al 2015;Vettraino et al 2015). A sentinel nursery ("in-patria" plantings sensu Eschen et al 2018) is defined as a site where native traded plants are planted without phytosanitary treatments in their region of production (exporting country) and monitored to identify pests and pathogens which could be spread with the trade of those plants outside of their native range (Vettraino et al 2017;.…”

“…In this paper, we also consider the sentinel arboretum ( Fig. 3) (included as "ex-patria" plantings sensu Eschen et al 2018). Though not specifically designed as an early warning tool to detect potential plant pests or pathogens, arboreta and botanical gardens can offer another opportunity for sentinel research and contribute valuable information about novel pest-host associations (Britton et al 2010;Tomoshevich et al 2013).…”