As you may all be aware, despite the efforts of certain sectors the Oak Processionary moth continues to spread. This will be of no surprise to many of us! As you know there have been control efforts over the years, most recently the focus being to reduce the rate of spread of the moth. Most (but not all) current effort utilises Bacillus thuringiensis var. kurstaki, this sprayed on oak trees targeting young instar larvae. The issue with Bt is that it is not specific to Oak Processionary and impacts on the larvae of a wide range of Lepidoptera species that feed on oaks (and possibly in the understorey/on the ground) at the same time. We are therefore, extremely concerned about the potential negative impacts on biodiversity.
We have been working in the background over recent years, for example attending various meetings and workshops with a wide range of interested parties (such as Forestry Commission, Defra, local councils etc.), and have had more detailed discussions with Defra and FC. The thrust of our message is to push a ‘learn to live with’ approach to the management of Oak Processionary. We don’t think we are quite there yet, but this approach is now being discussed in earnest – all very positive. However, it is acknowledged that there will still be control of Oak Processionary in the future as there is unquestionably a human health issue. We (BC) would like to see this control being localised to areas of high human presence, such as around schools, hospitals, car parks etc., but at a much lower level elsewhere, particularly as the moth pushes out into the wider countryside. In early 2016 we produced a position statement which is on our website https://butterfly-conservation.org/files/position-statement-on-the-oak-processionary-moth.pdf
As this moth spreads, more people/organisations will become involved. This will include an increasing range of land owners/site managers etc. Clearly we would like them to take the potential impact on biodiversity into account should control measures be considered. Defra are also keen to ensure that potential impacts on biodiversity are considered in that decision making process. As a consequence we are at the early stages of looking into developing a potential tool to help land owners etc. with the decision making process (human/animal health and possibly also tree health are also likely to be part of the bigger picture). This tool would utilise data from the National Moth Recording Scheme (NMRS) (including micro-moths if full coverage of the south east region were to become available) and the Butterflies for the New Millennium (BNM) datasets. The resolution at which this tool would work is yet to be determined, but our currently favoured resolution is at the 1km level. Broadly, we plan to assess the species across the south east region (Sussex, Kent, Essex, Hertfordshire, Middlesex, Buckinghamshire & Berkshire), buffering grid cells to account for habitat use and dispersal. We will then calculate a relative risk score of spraying within the given grid square based on a score given to each species. The species scoring will be weighted according to priority (threat) level, oak feeding, larvae present at time of spraying etc. Individual species or records will not be identified, but the scores for each grid cell will be displayed to land owners considering spraying in categories based on the ecological risk. Once the tool has been tested, it is expected that this will be made available as an online web tool – it is anticipated that this will be available to the public and hosted by Defra.
As mentioned above, please bear in mind that control measures will continue, and without this tool impacts on biodiversity are unlikely to be included in the decision making process of when to spray/when not to spray, with the exception of a relatively few sites. We therefore believe this will be a useful way forward, and will also help raise the profile of moths as useful biodiversity indicators.
Further information on Oak Processionary, including a map of its recent distribution, is given at https://www.forestry.gov.uk/oakprocessionarymoth and for nest distribution in 2018 see https://www.forestry.gov.uk/pdf/NestSurveyStatus_Infestation_20180723.pdf/$FILE/NestSurveyStatus_Infestation_20180723.pdf. For the results of pheromone trapping in 2017, see figure 4 in https://www.forestry.gov.uk/pdf/OPM2017operationalreportfinal.pdf/$file/OPM2017operationalreportfinal.pdf
As the above proposal involves a novel use of the NMRS and BNM data we felt we should make you aware of this potential development. We are happy to discuss further if you would like and if you have any concerns about the above proposal please do get in touch. Thank you for your time on the above and apologies for the long message.
Mark Parsons & Katie Cruickshanks