Eamonn Wall attended the Arboricultural Association’s annual conference, held at Warwick University on the edge of Coventry in September.

THIS year the Arboricultural Association’s (AA) Conference followed a new format with two days of presentations on the Monday and Tuesday and a field trip to Coombe Abbey Park estate on the Wednesday. There was also a tree-climbing competition and tree-planting event back at the university on the Sunday. The new format seemed to work well and it was announced that the conference would be again held here at Warwick University in 2024.

Around 400 delegates attended over the four days, with 85 delegates on the visit to the lovely Coombe Abbey grounds. There were 26 exhibitors located in and around the main auditorium. Unusually, the conference programme did not give any details as to who the speakers worked for or indeed who the 400 delegates worked for. Certainly it would have been useful to have had this information.

Day One

Forestry Journal: Warwick University hosted the conference earlier this year. Warwick University hosted the conference earlier this year. (Image: eA)

John Parker, the AA’s chief executive, opened the conference on the Monday, followed by nine speakers, a quickfire discussion with four mini presentations, and then the choice of attending a workshop on various topics. This format was repeated on the next day.

First up was Andrew Benson from New Zealand who reviewed a research project about trees and overhead utility cables that showed that large trees, heavily pruned, provided better ecosystem services than small trees. Kristin Moldestad, who works as an arb consultant and lecturer, outlined that no oaks over 200 cm girth could be felled without permission in her native Norway. She also part wrote a book on the identification of roots, which was interesting to hear about. The books were for sale at £25 and I bought one. Then Benoit De Reviers from France went through an interesting bunch of slides on bracing trees and how trees had reacted to the bracing over time. Both cables and strapping examples were shown and the more recent use of creating anchor points with bolts.

The next session got going with a very experienced presentation on the science and management of Massaria disease of London plane trees by Greg Packman. He has inspected about 90,000 plane trees. The disease is a soft rot and is considered a weak parasite, usually attacking poorly trees. It was discovered in Germany in 2003 and first appeared in the UK in Hyde Park in 2008. It generally is found in smaller-edge canopy branches where it can weaken branches, but it does not kill trees. Badly infected branches in areas where failure is a high risk to the public should be removed, but it is very important to leave a stub and not cut at branch bark ridge as this removes the natural defensive barrier the tree has put in place. 

Forestry Journal: Cecily Withall, centre, was presented with her award for Young Arboricultural Professional of the Year. Cecily Withall, centre, was presented with her award for Young Arboricultural Professional of the Year. (Image: eA)

Then Richard Hauer from the USA gave us a talk about the emerald ash borer where active management was better than no management. They sometimes inject trees to save them. They also found that crime rates increased where a lot of tree cover was lost, which he thought was because such neighbourhoods fell into a sorry state and this attracted more crime. This disease session came to a close with a presentation by Jon Hartill who now works in Sweden. His presentation on Meripilus in beech focused on retaining infected trees and that crown removal to reduce risk of failure often caused the disease to expand as new dead wood resulted from the pruning. Not everyone agreed with him. He also used tomography to examine roots via Radix, but some people questioned the use of this as Meripilus decays the underside of roots, so is perhaps not detectable.

The next session started with some prizegiving for best student followed by two presentations chaired by Jim Smith. Barrister Elizabeth Nicholls introduced us to the legal implications of Biodiversity Net Gain (BNG), which becomes law in England from January 2024 (having been pushed back from November 2023). 

Going forward, any planning applications for development works must include a survey of all the biodiversity on the site and how this will be improved. It has to be improved or expanded by 10 per cent and this has to last 30 years. Biodiversity credits can be bought if biodiversity improvements cannot be made. Then Emilie Wadsworth outlined the Central Scotland Green Network, which is a planning initiative that came into being in 2009. The most recent version was confirmed in 2023 to last to 2033. It has ambitions of increasing tree cover and green transport, and restoring derelict and vacant land. CSGN is managed by the Green Action Trust which is the modern version of its predecessors, the Central Scotland Woodland initiatives. The later afternoon session comprised an international panel discussion on challenges and opportunities in global arboriculture by four speakers chaired by Kevin Frediani from Dundee University Botanic Garden.


Paul Barber from Australia outlined the increase in tree pests and diseases also came at a time when the public’s appreciation for trees was growing; but with early retirements and poor training there was a decrease in professional capacity to deal with tree issues. This has led to an increasing demand for good tree data. He was optimistic and felt the increasing use of digital learning aids – remote sensing and (a new one on me) Internet of Things (IOT) which is basically dynamic data; data being collected and used right away via the internet – would help success.  

Yana Bobrova from Ukraine outlined by video the loss to the war of a young arboricultural student. She also ran through a small survey she had carried out among tree workers in Ukraine and outlined the low tree cover and few conservation habitats in her country caused by industrial farming. 

Forestry Journal: Viewing large veteran parkland oak tree with Coombe Abbey Hotel in the distance. Viewing large veteran parkland oak tree with Coombe Abbey Hotel in the distance. (Image: eA)

Lee Mueller from the USA concentrated his ten minutes on invasive pests and diseases and mentioned again the emerald ash borer and now the risk from the Asian long-horned beetle. He felt that climate issues caused people to be more appreciative of trees and to want to solve environmental issues. 

Jon Hartill spoke again about the damage pruning does to trees causing sapwood dysfunction. The workshop sessions followed, which were repeated on the next day (I review them later). 

The exhibitors provided a wine reception followed by evening gala dinner. A pleasant evening was had by all.

Day Two 

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Day two followed a similar format,  chaired firstly by Michelle Ryan, the chairperson of the AA. 

Paul Barber was on again and here reviewed the use of remote sensing for BNG. He also reviewed the Vegetation Condition Index (VCI). 

Lee Mueller spoke about technological advancements in tree inventory and monitoring, which can help to speed up tree surveys and locate possible areas/positions for new tree planting. He mentioned that humans were poor data collectors, but good analytical players. Tree surveys are often subjective and thus hard to compare over time as surveyors’ views change too. Ground-based LIDAR and mobile laser scanners were discussed. 

Martin Dobson followed with a presentation full of slides showing trees that had fallen onto cars and buildings, which woke everyone up a bit. His paper on litigation in tree failure cases outlined the usual items of care of duty, test of foreseeability, and ‘should have known’ view by the courts.

Keith Sacre of Barcham Trees chaired the next session of three speakers. 

Jill Butler spoke about ancient and veteran trees and the Ancient Tree Register and the European Champion Tree Forum. 

Jason Hasaka of Bartlett Trees outlined all the work they had done researching the Allerton oak and re-propping it. The tree dates from 1440. The old props were left in place as their removal would have caused damage and they were also still doing some propping. 

Emma Gilmartin is the ancient tree leader at the Woodland Trust and spoke about three research projects the trust is involved in. Its ancient tree inventory is the database of trees that the general public notifies its members about. It has 170,000 trees – mostly oak in England. 

The final three main presentations kicked off with Kate Lewthwaite presenting on another Woodland Trust citizens project – re-coding nature’s natural calendar, phenology. The first person to record springtime was Robert Marsham in 1736, recording 13 trees and shrubs. The trust’s project started in 2000, mostly spring records of 69 species which do show a general spring burst earlier. Since 1894 the difference is 8.4 days. This can be a problem for birds as caterpillar populations may come too early for bird nesting and feeding requirements. The measurement of the onset of autumn is now being recorded too, first frost, first show of tinted leaves and bare tree. 

The Tree for Cities duo was up next, with Louise Purnell outlining their 30-year-old tree-planting scheme. She went through the five-point plan they have for organising tree-planting projects from inception to completion. Cat Walker then went through the research work they have done to see what the users have gained from the tree-planting events. They also use a nature connection index. 

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Jim Mullholland took us through the surveying for bats project he has been working on.

The international panel session followed. 

Kristin Moldestad was up again, speaking about a new arb course just set up in Norway. She outlined challenges of climate change; more wind and rain, floods and landslides, new pests and diseases, and new alien species arriving in Scandinavia.

There is a lack of knowledge of urban trees (rising ground levels due to developments, much excavations in the root zones), however, a new act in 2009 should help with improved regulations for trees in cities and towns. The arb course is a part-time two-year course at a vocational college. Andrew Benson spoke about more demand for housing, but also minimum industry standards, alongside 17 very good tree-work manuals and a registered consultant programme.

The workshop that followed included six sessions and the seventh being the continuation of the international panel discussion above. 

The sessions were on Succession in arboriculture – Michelle Ryan and Luke Fay; Regulating work to trees – the legal side – Charles Mynors; Major Oak Gallery Guided Tour – Reg Harris; Tree planting: more than the numbers – Keith Sacre and Ben Cross; Detection dogs in arboriculture – Ivan Button and Sika; and Registered consultants scheme – Simon Richmond. I attended the trees and law workshop which saw Charles Mynors reviewing the legal history to TPOs and felling licences and coming up with some suggestions for simplification. 

It is unfortunate that the legal details of these laws vary between England, Wales and Scotland as the penalty for illegal felling in England is open whereas it is max £5,000 per tree in Scotland, which Charles seemed to forget.

Day Three 

Forestry Journal: Is this Dryad’s Saddle? Not everyone was sure.Is this Dryad’s Saddle? Not everyone was sure. (Image: eA)

The next day we were off to Coombe Abbey Park. We met at 10 am for coffee and introduction by the park manager. The site comprises a very old hotel and then a large 500-acre site, boasting a river and small lake, lime avenue, large parkland with veteran trees, an arboretum, a Go Ape area, garden, meadows and woodlands. Half a million visitors enjoy the park annually. 85 delegates were split into four groups and we headed off to look at veteran trees, woodland trees, the arboretum and enjoyed an interesting discussion from Go Ape and the issues to be considered in running these schemes vis-à-vis climate change and in particular tree diseases affecting chosen trees. 

Forestry Journal: Recent storm damage to degraded veteran ash tree. Recent storm damage to degraded veteran ash tree. (Image: eA)

This is now an issue with ash dieback in this park and Phytophthora ramorum in larch elsewhere in Aberfoyle. The parkland trees had been laid out by Capability Brown, but the site dates from the 11th century. We saw a huge Sorbus domestica, which is a champion tree that had a large limb break out of it this past winter. The tree officer was considering some crown reduction to help retain the tree. This approach was also being considered for some of the other veteran trees in the parkland.

This was an enjoyable conference and the new format seems to work very well indeed.