Oak processionary moth

A recent research project has focused on finding the best methods of capturing the moths in order to determine their population and rates of spread

News from Forest Research: February 2012

Oak processionary moth

As well as being a serious defoliator of oak trees, OPM also poses serious public health issues. The hairs of OPM larvae can cause severe allergic reactions in both animals and humans, including dermatitis, conjunctivitis, respiratory problems such as pharyngitis and asthma, or, more rarely, anaphylactic reactions.

The oak processionary moth (Thaumetopoea processionea L.) is a serious defoliator of oak trees and the hairs carried by the older larvae pose a significant risk to human and animal health. The spread of this non-indigenous pest needs careful monitoring and a recent research project has focused on finding the best methods of capturing the moths in order to determine their population and rates of spread.

Oak processionary moth (OPM) is widely distributed in western, central and southern Europe, and was accidentally introduced into west London in 2006 on young oak trees imported from Europe. A visit by Forest Research staff to Saxony-Anhalt in Germany highlighted its impact on tree health, with widespread and intense defoliation and tree mortality observed where oak trees had been damaged over a 2–3 year period.

Forest Research has been monitoring the spread of OPM since its introduction into the UK, using ground surveys to locate nests and a network of pheromone traps to catch male moths. However, over the past five years it has become clear that the network of pheromone traps has not captured as many moths as expected, nor has it proved particularly effective at monitoring their spread. As a result, current research is focusing on how to improve the trapping techniques for OPM.

In the summer of 2011, Forest Research worked in collaboration with The Royal Parks (Richmond Park), the Royal Botanic Gardens at Kew, the arboricultural company Gristwood and Toms Limited, and the University of Derby on a joint project to evaluate a variety of parameters that might influence the effectiveness of pheromone trap captures.

The project has demonstrated that the type of trap used, its positioning in the tree canopy, and the source and chemical composition of the pheromone lure are all important in determining the numbers of moths caught. These findings will influence the protocols used in the future for monitoring the spread of the moth. A summary of the results is currently being written up for publication.

Further information on OPM

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This and other news stories can be found in the Winter 2011/2012 issue of FR News, our online newsletter.