Controlling Dutch elm disease on the Isle of Man

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The purpose of this page is to encourage interested parties, including the Isle of Man Government, commercial third parties such as BlueSky and interested individuals to confer and if possible work together to make the best use of available modern technologies so as to improve the chances of keeping Dutch elm disease on the Isle of Man at or below its current level into the future. It may even be possible to significantly reduce its impact.

Elms on Mann

The Isle of Man is home to around 250,000 elm trees - the largest and most concentrated healthy population of mature elm remaining anywhere in Europe. There are huge elms on Mann that no longer have any equivalents anywhere else in the British Isles, nor probably in Europe as a whole. These represent a great natural asset for the island, a tourist attraction and material resource.

The virulent strain of Dutch elm disease arrived on the island in 1992. In contrast to mainland Britain where, from its arrival in 1967, the disease rapidly spread out of control and destroyed upwards of 25 million trees and became endemic, on Mann a combination of isolation, climate and - crucially - immediate, strong and consistently applied Manx government action- has meant that a quarter of a century later, only around 1,750 trees from the stock of elm on the Isle of Man have been lost. This has not been achieved without sacrifice and determination. The Manx Forestry authorities have - and exercise - the right to immediately fell and burn infected trees anywhere on the island, where appropriate compensating landowners.

Despite their best efforts, by 2009, the disease had become firmly established on the Isle of Man and there was a recognition in the control team that the campaign against DED was moving into a new phase - from containment to control.  This being so, there was a significant risk that if key conditions changed, the campaign might fail to cope unless it was restructured and more effective methods adopted.

Key risks

These key conditions include the risk that the largest of the three elm bark beetle species (scolytus scolytus) might arrive on the island from the British or Irish mainland. Were that to occur, it might be game over for the Manx elms, as the larger beetle can host more fungal spores. It takes up to 10 feeding S. multistriatus or S. laevis females to kill a full-sized tree, but the same result can be wrought by a single s. scolytus– and this species generates two broods every year. Except under favourable climatic conditions, the others only produce a single brood.

Climate change could also alter the effectiveness of the Manx campaign, but increasing temeperatures have contrary effects on the beetle, the fungus and the trees, so this is difficult to assess.

However, perhaps the most critical condition is the maintenance of a dependable level of legal, financial and moral support from the Manx government. A consistent long-term commitment must be maintained. On Guernsey, the disease was brought down to a very low level, but the authorities then relaxed their vigilance and lost the fight.

Traditional methods of field-walking and submission of paper 'spotters' reports' had long been effective locally, but they were slow and did not prevent the disease becoming established. The three Dutch elm disease reports commissioned on the island (Fairhurst, 1982, Greig, 1992 and Rose 2000) all recommended that a census be taken of all the elms of Mann. Due to the size of the task and the traditional methods employed, this had only partially been completed by 2009. More modern methods of monitoring, enumeration and control need to be encouraged. 

Dissertation


In 2009, I produced a dissertation on "Dutch elm disease on the Isle of Man: Identifying ‘danger-spots’ using an agent-based model" as part of a Master's Degree in Geographical Information Science at Birkbeck, London.  I used GIS, statistics and a computer model to identify areas on the island where outbreaks of the disease were likely to prosper and generate a bloom of infection that might burst out of control across the island.

To support the research, I spent a few days on the Isle of Man and visited Doug Chalk and Jimmy Lee at the Forestry Division, Department of Agriculture, Fisheries and Forestry, St John’s Depot and Rob Clynes, Senior Cartographer at the Isle of Man Survey Mapping Service, Department of Local Government & the Environment, Douglas.

The dissertation was awarded a distinction, and spawned four published papers (2009, 2010, 2011, 2015) and presentations in Sydney and London. 

The full dissertation may be downloaded HERE

Dedicated MSc webpage HERE

Opportunities presented by modern technologies 

At the time, I encouraged the Manx authorities to look at new technologies that might help speed along the elm census and the reporting of disease outbreaks. It is encouraging to see that the forestry authority has have since embraced crowdsourcing to assist in the early identification of diseased and 'brood' trees. The Open Elm Project, an open-source mobile phone app, allows walkers to record instances of diseased elms directly into a Manx government database, greatly shortening response times. This does, of course depend upon the assistance of an active and civic-minded citizenry, and should not be seen as a cheap replacement for specialist spotters.

I spent some time investigating tree species identification from spectral analysis of aerial photography. It has to some extent been possible to do this at least since the 1960s , but this depended upon human interpreters. Since that time, the analysis has become increasingly turned over to computers and LiDAR, hyperspectral, multi-spectral and panchromatic analysis have been added to the toolset. The activity has remained very much the preserve of a very small number of instiitutions with deep pockets. In 2009 the few avaiable tools (e.g. ENVI) ran to tens of thousands of pounds, with no UK student deal, and there were a handful of installations in the UK. Combined with the steep learning curve required for the discpline, this meant that I was not able to seriously pursue spectral analysis for species identification within the limited time available for the dissertation, However, in the years since my MSc, the discipline has advanced significantly, stimulating intense academic and commercial interest. Results, and affordability, are rapidly improving.

Bluesky , a commercial company based in Leicestershire, is now collaborating with Forestry Commission and the University of Leicester on the use of airborne mapping systems to identify diseases in trees to protect the British landscape,exactly the sort of collaboaration I was anticipating while doing my MSc. They have also created the first 'National Tree map', " the most detailed dataset of its kind ever produced. With coverage across the whole of England and Wales, NTM provides a unique, comprehensive database of location, height and canopy/crown extents for every single tree 3m and above in height."

Bluesky make intensive use of another rapidly-developing technology - the drone. Drones are already being widely used across the globe to rapidly cover large areas of dense forest and understand woodland habitats.

So there is no reason why drones should not also be used across Mann to cheaply provide high resolution imagery of at-risk areas whenever it is needed. A purely visual inspection of the imagery would permit rapid and easy identification of diseased crowns and immediate treatment of the affected trees. The drone would allow all other elms in the vicinity to be surveyed and appropriately treated at the same time. This would extend and greatly increase the effectiveness of the control measures, because infected trees could be identified and felled at a very early stage,within days of their infection. This might permit more fine-tuned control measures, with only the directly affected portions of the tree being felled and destroyed rather than the entire tree.


A more scientific analysis of the imagery, perhaps in collaboration with a commercial partner, would provide enhanced opportunities for completing the elm census and for understanding the health of the entire woodland canopy.

I would therefore encourage the Manx Forestry, Amenity and Lands Directorate to seriously look at adding a set of drones to the toolbox of the team responsible for Dutch elm disease control. It may be sensible to begin with a detailed survey of a limited area with a well-documented tree population (e.g.an arboretum)for calibration and training purposes. If the Directorate's freedom of action is limited by budgetary contraints, these might be eased by seeking a sponsorship deal from likeminded organisations or individuals.

I am not affiliated in any way with BlueSky or any other organisation mentioned on this page. My interest is solely to further the preservation of the elms of the Isle of Man.


I would be happy to assist in any way I can.