Managing tree pests and diseases in urban settings: The case of Oak Processionary Moth in London, 2006-2012

Oak Processionary Moth (OPM: Thaumetopoea processionea) is long established in mainland Europe, where it is known to cause defoliation of oaks which can significantly weaken affected trees, leaving them vulnerable to other stressors. OPM also poses a threat to public health through skin and respiratory irritation caused by the poisonous hairs on the caterpillars. Official confirmation that OPM had been found in the UK for the first time in London in 2006 marked the beginning of a long and difficult campaign to eradicate this pest from a largely urban setting. Following its continued spread, however, the outbreak was eventually judged impossible to eradicate. In 2010, a policy of containment was adopted to minimise the population, spread and impacts as much as possible. Despite this, OPM continues to pose a threat to tree and human health in London. This paper examines how OPM was managed in London and asks why eradication proved so difficult. It explores the governance and management challenges faced by those involved in the attempted eradication campaign and assesses the extent to which the specifically urban setting of the outbreak intensified these difficulties. This paper draws on documentary sources and a series of 20 semi-structured interviews conducted by the authors with experts and stakeholders involved in managing the London OPM outbreaks between 2006 and 2012. Three key challenges were identified: assigning statutory responsibility for urban trees; co-ordinating the stakeholder and landowner response in a complex urban setting; and assessing and managing combined risks to trees and people. (C) 2015 Elsevier GmbH. All rights reserved.