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This project aims to improve the effectiveness of commercially available pheromone traps for monitoring populations of oak processionary moth (OPM), and to integrate their use within the wider management programme for this important forest pest.

Research objectives

Specific research objectives are to:

  • determine the optimum placement of traps within the tree canopy
  • compare the efficiency of different types of traps and pheromone lures (sex attractant) obtained from different sources
  • determine the influence of other factors, such as habitat, tree density and weather conditions, on numbers of moths caught
  • establish relationships between the numbers of moths caught in pheromone traps and OPM population densities in the surrounding area.

Results so far

Field trials have shown that the type of trap (Delta or funnel), the pheromone lure and the position of the trap in the tree can all affect the numbers of OPM caught in pheromone traps, and therefore influence the quality of monitoring. Significantly more male moths were captured in traps placed in the upper canopy of oak trees (77%) compared with the mid-canopy (19%) or lower canopy (5%). Funnel traps also caught six times more male OPM than Delta traps, and chemical analysis revealed considerable differences between three commercially available pheromone lures.


This project started in 2011 and is ongoing.

Related Resources

Tools and Resources webpages on OPM

Native species that can be mistaken for OPM

Other oak defoliators

Pest Risk Analysis of OPM


Williams D T, Straw N, Townsend M, Wilkinson A S and Mullins A. (2013). Monitoring oak processionary moth Thaumetopoea processionea L. using pheromone traps: the influence of pheromone lure source, trap design and height above the ground on capture rates. Agricultural and Forest Entomology 15, pp126—134.

Straw N, Williams D T. & Tilbury C. (2013) Monitoring the Oak Processionary Moth with Pheromone Traps. Forestry Commission Practice Note 20. Forestry Commission, Edinburgh.

Williams D T and Jonusas G. (2019) The influence of tree species and edge effects on pheromone trap catches of oak processionary moth Thaumetopoea processionea (L.) in the UK. Agricultural and Forest Entomology 21: 28-37.


Dr David Williams

Funders and partners

This research is currently funded by the Forestry Commission under the Programme Advice and Scientific Support for Tree Health.

Early trials work was also part-funded by Defra

Forestry Commission policy
This research underpins the evidence base for the delivery of healthy and resilient forests and wider ecosystems which is part of the Tree Health and Plant Biosecurity Action Plan.

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David Williams