Conservation & Ecology


A cluster of OPM larvae on an oak trunk “ 92 I PC APRIL/MAY 2014


OPM is a legally notifiable tree pest, so suspected sightings must be reported - no work may begin on a suspected infested tree until the Forestry Commission has inspected it


OPM - KEY FACTS • Native range - Southern Europe


• Northernmost presence - northern Germany and Netherlands


• First introduction to UK - probably 2005, to West London, probably as eggs previously laid on semi-mature oak trees imported from continental Europe


• Habitat - almost exclusively oak trees. Will attack other broadleaved species if preferred oak-leaf diet is lacking


• Distinctive feature 1- Larvae move about in nose-to-tail processions, hence the name


• Distinctive feature 2 - white, silken webbing nests and trails on oak trunks and branches. Larvae rest in these when not feeding, and during pupation into adult moths in early summer


• Not to be confused with - pine processionary moth (no evidence of establishment in UK)


A small, spent nest with cast larvae skins ©Richard Gill/Sheffield City Council


A large, disintegrating, spent nest with cast larvae skins. Crown copyright/Forestry Commission


requiring its removal, and you must follow the Good Practice Guidance after that has been done. Sightings are best reported via:


- our Tree Alert app or on-line reporting form - see www.forestry.gov.uk/treealert


- the Local Council. A directory of councils’ reporting contacts is available under ‘Reporting suspected cases’ at www.forestry.gov.uk/opm;


- opm@forestry.gsi.gov.uk


We particularly welcome sighting reports with clear photographs to aid identification, and precise locations - OS grid references are ideal. Trees should be marked to ensure we inspect the correct ones We monitor male moths with a network of


pheromone traps, which can provide clues to where we might expect to find OPM the following year. There are restrictions on the handling of


oak material, such as felled trees and prunings, in the affected areas. These are intended to prevent accidental spread of


OPM, for example, by larvae or adult moths which might be present in felled trees or prunings. The restrictions are set out in detail in the Good Practice Guidance, but key points are:


- no work may be carried out for twelve months on a tree which has had OPM presence confirmed and treated, to allow time to ensure that it is free of OPM. If the work cannot be delayed this long, e.g. for safety reasons, the arisings must be chipped before removal


- oak material in the affected areas should be kept on site, if possible, until movement no longer risks spreading the pest. If this is not possible, the arisings must not be taken outside the affected areas without first consulting the Forestry Commission’s Plant Health Service. Email plant.health@forestry.gsi.gov.uk or telephone 0300 067 5155.


If you bring in tree surgeons, make sure


they are reputable, such as members of the Arboricultural Association, and check that they are familiar with these requirements.


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