What is Oak Processionary Moth (OPM) and why survey for it?
- OPM originates from continental Europe and was first found breeding in Britain in 2006, in west London, as a result of the accidental importation of its eggs on oak trees for planting.
- The adult moths are harmless but the caterpillars have a defence in the form of minute barbed hairs containing a chemical that causes unpleasant skin rashes and, less often, other allergenic symptoms in humans. Rashes may be persistent and painful and domestic animals such as dogs, cats and horses can also be affected.
- OPM caterpillars live in groups on oak trees from April or May to June or July. Numbers can build into 'plagues' which cause disruption to human activities and extensive defoliation of oaks to the detriment of the trees. Before they are fully grown, each group builds a silken nest (or tent) on a branch or trunk in which they shelter and pupate.
- The hairs are ejected when the caterpillars sense a possible threat and are easily carried on local air currents. Their cast skins contaminate the nests, which may take months or years to break down after the moths have emerged. During this time the hairs retain their chemical irritant.
- OPM had already been through several generations in west London before its discovery and it was able to become established across London and into the Home Counties.
- A population of OPM resulting from the importation of a single oak tree to west Berkshire in 2010 was successfully eradicated (see below).
- In spite of changes to the importation legislation covering tree pests carried on planting stock, in 2019 OPM caterpillars were found at 70 planting sites scattered across a wide area of Britain. The population in southeast England continues to spread and increase, and consequently OPM could occur almost anywhere.
- Although severe symptoms are rare, the health hazard and tree health issues presented by OPM means that local authorities and other landowners are obliged to undertake measures to control it in order to protect people and trees from its effects.
- Due to the growth in the size of the affected area, FC support is now far from comprehensive.
- Further information on OPM can be found at https://www.forestresearch.gov.uk/tools-and-resources/fthr/pest-and-disease-resources/oak-processionary-moth-thaumetopoea-processionea/, https://opmhub.fera.co.uk/ and https://treecouncil.org.uk/what-we-do/science-and-research/oak-processionary-moth/
What can I offer?
- Surveys for the larval nests in oak trees, inspections of small trees for egg batches and pheromone trap monitoring, all carried out by well-trained and experienced surveyors.
- Site-specific advice on OPM control, cost-effectiveness and options that minimise the effects on local biodiversity, and assistance with management planning.
- Staff training. An illustrated talk and field demonstration of where, when and how to spot nests and egg batches effectively and safely.
- 16 years’ experience (2006 onwards) of surveying for OPM in the public sector, as framework contractor holder and subcontracting Plant Health Inspector for the Forestry Commission and as a lead contractor for local authorities.
- Lead contractor for the Forestry Commission in the first successful campaign to eradicate an established population of OPM in Britain, in Pangbourne, West Berkshire.
- OPM consultant and surveyor for Guildford Borough Council since 2017.
- Understanding of the issues caused by OPM, and wide knowledge of surveying, monitoring and control techniques, and the bionomics of OPM.