Abstract
The ornamental plant trade has been identified as a key introduction pathway for plant pathogens. Establishing effective biosecurity measures to reduce the risk of plant pathogen outbreaks in the live plant trade is therefore important. Management of invasive pathogens has been identified as a weakest link public good, and thus is reliant on the actions of individual private agents. This paper therefore provides an analysis of the impact of the private agents’ biosecurity decisions on pathogen prevention and control within the plant trade. We model the impact that an infectious disease has on a plant nursery under a constant pressure of potentially infected input plant materials, like seeds and saplings, where the spread of the disease reduces the value of mature plants. We explore six scenarios to understand the influence of three key bioeconomic parameters; the disease's basic reproductive number, the loss in value of a mature plant from acquiring an infection and the cost-effectiveness of restriction. The results characterise the disease dynamics within the nursery and explore the trade-offs and synergies between the optimal level of efforts on restriction strategies (actions to prevent buying infected inputs), and on removal of infected plants in the nursery. For diseases that can be easily controlled, restriction and removal are substitutable strategies. In contrast, for highly infectious diseases, restriction and removal are often found to be complementary, provided that restriction is cost-effective and the optimal level of removal is non-zero.
Highlights
Increases in the movement of people and traded goods as a consequence of globalisation have led to growing concerns about the threat posed by invasive species. especially invasive pathogens of humans, plants and animals (e.g. Anderson et al, 2004; Waage and Mumford, 2008; Perrings et al, 2010; Hulme, 2014; Dalmazzone and Giaccaria, 2014)
Recent disease outbreaks in plants, such as the Chalara fungus (Hymenoscyphus pseudoalbidus) affecting ash trees across Europe (Pautasso et al, 2013) and the oomycete Phytophthora ramorum affecting many plants including larch in Europe (Brasier and Webber, 2010) and oaks in the US (Rizzo et al, 2002), have focused attention on the policy options to reduce the risks of similar plant disease outbreaks occurring in the future, and the management options to reduce damage from newly established pathogen populations
These disease outbreaks have raised concerns about patterns of plant trade, which has been identified as a key introduction pathway for invasive pathogens (Santini et al, 2013), and on the need for a more prominent role of the private sector in biosecurity practices to mitigate existing risk (Liebhhold et al, 2012)
Summary
Increases in the movement of people and traded goods as a consequence of globalisation have led to growing concerns about the threat posed by invasive species. especially invasive pathogens of humans, plants and animals (e.g. Anderson et al, 2004; Waage and Mumford, 2008; Perrings et al, 2010; Hulme, 2014; Dalmazzone and Giaccaria, 2014). Prior bioeconomic research on the plant trade has focused on its role as a significant pathway to the introduction of potentially exotic invasive plants, exploring the use of taxes or annual license fee to reduce this risk and cover the expected environmental damages (Knowler and Barbier, 2005; Barbier et al, 2011). Implementing these market-based instruments is challenging due to the lack of support among stakeholders in the industry (Barbier et al, 2013; Touza et al, 2014). We find that if the disease spreads faster than the ability to control the disease, removal and restriction complement each other whereas if the disease is controllable, removal and restriction become substitutes
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