Pests in the City: Managing Public Health Risks and Social Values in Response to Oak Processionary Moth (Thaumetopoea processionea) in the United Kingdom

Oak processionary moth (Thaumetopoea processionea) or OPM was accidentally introduced into London on imported oak trees and now poses a threat to the future of oak in the urban landscape. Early attempts at eradication of the moth failed and significant resources have since been spent by government on monitoring and controlling OPM (through the use of insecticides or bio-pesticides) as it spreads into new areas. OPM is regulated in the UK to minimize risk of new introductions and reduce spread. Surveying for OPM and issuing of statutory notices for control is based on a geographical system of core, control and protected zones. While OPM will defoliate the trees leaving them vulnerable to other pests and diseases and stress factors, the caterpillars can also harm people and animals via tiny urticating hairs with the potential for dermatological or respiratory impacts. However, the biggest threat to the iconic British oak may be that the perceived risks associated with OPM, and costs of management may lead land managers to fell their oak trees, and not plant oak in the future. There is a need to better understand awareness, risk perceptions and decision-making around OPM management. We use a conceptual framework to explore decision-making and the trade-offs between the social, economic and ecological values associated with oak trees, and assessment of risk related to both the moth and control options. Twenty nine interviews were conducted in two London boroughs and across Greater London and in some surrounding counties covering a range of land types (e.g., parks, school grounds, amenity areas and private gardens) with infested or non-infested oak. We found a lack of evidence of human health impacts from OPM although land managers were concerned about public duty of care and potential reputational damage if they do not manage OPM. To address the challenges of dealing with OPM, land managers were taking a risk-based approach and managing OPM where it posed the highest potential risk to people. Respondents expressed strong emotional attachments to oak but it also has high biodiversity value which can lead to difficult decisions about management options. A risk-based approach moves beyond a ‘one-size-fits-all’ control method and focuses available resources where they are most needed and socially acceptable. An approach that allows for multiple values and perspectives on risk may provide a more sustainable long-term option for OPM management to ensure the future of oak in the city.