Every now and then in life you gain sudden clarity of vision about an issue; perhaps triggered by listening to someone erudite, reading something written with super clarity, or seeing it with your own eyes. In my case it is the latter and I’m worried – super worried in fact. I am not prone to exaggeration.
I recently visited Richmond Park, the largest of London’s Royal Parks. It is a vibrant place full of ancient trees, home to several herds of Red Deer, and it teems with joggers, dog walkers and families. Around it on all sides is the highrise metropolis of London including Wimbledon, Putney, Richmond and Roehampton. In a few weeks it will be host to the Olympic cycling road race. Most visitors scarcely notice the metal fencing and red tape around the occasional oak tree; presuming probably that the tree may have a dangerous branch or needs extra protection from the browsing deer. But they would be mistaken.
I saw with my own eyes the oak trees of Richmond Park infested with the caterpillars of the oak processionary moth (OPM) Thaumetopoea processionea. The caterpillars can cause serious damage to trees by defoliating entire canopies but this is a minor problem in comparison to their effect on human health. The caterpillars of the third to sixth instars have poisonous hairs or setae that carry a toxin that can cause serious irritation to the skin, eyes, nose and throat of humans and other animals. If inhaled they can cause respiratory distress, asthma and even anaphylactic shock.
The human health danger is scary in its own right but it is the consequences of the increasing spread of OPM that is my real concern. Three years ago the authorities at Richmond Park spent £50,000 in one season trying to control the pest but costs have been doubling every year, year on year! A decision was taken last year by all those concerned with OPM in London that eradication was not an option; instead aiming for containment. Meanwhile the moth continues to be found in an ever-increasing range within Greater London. An outbreak in Sheffield was successfully controlled, while a population in Pangbourne near Reading evaded extinction in 2011 and is currently being retreated. How long before the various authorities decide that it is no longer worth spending a six figure sum trying in vain to control OPM when all around them trees in private gardens are going uninspected by the unaware general public? Sadly it may take a child blinded or even a death being reported in the red tops, like the Daily Mail, before notice is taken. This is not a forestry problem – it is a human health problem!
While huge amounts of public money are being spent on attempts to control OPM with little effect, the pest is not yet at large among private gardens and larger forests. When, and it is surely ‘when’ and not ‘if’, OPM becomes widespread on private land then it will be the landowners that will be required by law (under the Plant Health (England) Order 2005) to report their presence and pay for their control. I can’t imagine any owner of an oak tree infested with OPM being pleased when required to spend up to £1,000 per tree. Forests in Holland and Germany have been so badly infected that they become out-of-bounds; the timber unusable for several years as the toxic hairs remain dangerously potent even on the forest floor.
I fear that OPM is a huge elephant in the room that everyone is wishing would go away. But, it is still early days in England, and if a German or Dutch arboriculturist were to see the extent of OPM in Britain they would surely urge us to try harder: to go for eradication across all of London rather than to give in now. Yes it will be expensive. Yes it will need co-operation between lots of different authorities. Yes the public will have to be involved too and be encouraged to report OPM in their gardens. Ignoring OPM is not an option – its spread is a disaster already happening – soon impacting our gardens, parks and forests across England unless action is taken urgently.
Further information on the Oak Processionary Moth (OPM)
Oak Processionary Moth – management implications
A looming threat to man and tree – a post I wrote in 2011
