The socio-economic challenges of managing pathogen evolution in agriculture

Abstract

Genetic resistance forms the foundation of infectious disease management in crops. However, rapid pathogen evolution is causing the breakdown of resistance and threatening disease control. Recent research efforts have identified strategies for resistance gene deployment that aim to disrupt pathogen adaptation and prevent breakdown. To date, there has been limited practical uptake of such strategies. In this paper, we focus on the socio-economic challenges associated with translating applied evolutionary research into scientifically informed management strategies to control pathogen adaptation. We develop a conceptual framework for the economic valuation of resistance and demonstrate that in addition to various direct benefits, resistance delivers considerable indirect and non-market value to farmers and society. Incentives for stakeholders to engage in stewardship strategies are complicated by the uncertain timeframes associated with evolutionary processes, difficulties in assigning ownership rights to genetic resources and lack of governance. These interacting biological, socio-economic and institutional complexities suggest that resistance breakdown should be viewed as a wicked problem, with often conflicting imperatives among stakeholders and no simple cause or solution. Promoting the uptake of scientific research outcomes that address complex issues in sustainable crop disease management will require a mix of education, incentives, legislation and social change. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.

Keywords: agriculture; economics; evolution; integrated disease management; pathogen.

Figure 1.

Direct and indirect economic benefits of implementing effective plant genetic resistance. The simplest value of genetic resistance arises from yield gains and reductions in crop mortality and crop quality losses. Indirect benefits can range from saving farm resources to wider benefits which can be broadly categorized as externalities and non-market benefits (e.g. reduced health costs, improved or maintained ecosystem health, and reduced evolution of pesticide resistance). Additionally, the productivity gains resulting from delayed pesticide resistance evolution can significantly benefit stakeholders by lowering investment in evolution management, which in turn generates spillover benefits by freeing resources for R&D investments that would further enhance the effective implementation of plant genetic resistance to pathogens.

Figure 2.

Reallocation of saved capital input. Effective plant genetic resistance can generate resource-saving benefits by freeing scarce resources for other productive on-farm activities. Heavy reliance on capital-intensive alternative disease control strategies (e.g. using pesticides) incurs additional capital costs for the farmer, including the purchase of pesticides and machinery, which could be reallocated to other production activities.

Figure 3.

Potential benefits of implementing plant genetic resistance management strategies. Assuming the time evolution occurs is measured in discrete units (e.g. years), the two plots show benefit per unit time in two scenarios (with and without resistance management interventions) where a new source of resistance is deployed in a crop species. Following deployment, resistance genes will have a period (T_N) where they will remain effective, even without management interventions that enhance durability. Although the benefits of management strategies at any given point in time may vary among stakeholders, for ease of illustration, we use a single curve representing best-practise stewardship management. As the adoption of management strategies is not costless, we have two components of costs: costs paid upfront (fixed costs, F) and ongoing-management costs, which are reflected in the net benefit. In both scenarios, the net benefit curve first increases but, after evolution evolves, it decreases because adverse evolution reduces the benefits per unit of time. Stewardship management has the benefit of prolonging the time until evolution occurs (by t = T_M − T_N), as compared with a no stewardship scenario.