LI Plant Health and Biosecurity Newsletter – Winter 2018

Abhainn Ashik to Yr Onnen by Ackroyd & Harvey. Photo: Gorm Ashurst. Source: The Ash Project

In this edition

LI biosecurity news

Dr Mariella Marzano of the Forestry Commission is carrying out research into the relationships between landscape and other professions – in particular, the way we think about plant health issues. She would like to hear a range of perspectives from practitioners. If you can spare 20 minutes to discuss your work with her, please contact her at

The LI Biosecurity and Plant Health Group is about to publish the first Biosecurity Toolkit for Landscape Architects. A long time in preparation, this toolkit follows the RIBA and LI Plan of Work, identifying key biosecurity issues to consider from landscape assessment to long-term management.

Save the date: The LI will run a CPD day in summer 2019 focusing on biosecurity and plant health from a landscape perspective. The day will focus on practical applications of current research and guidance, including a demonstration of the new Biosecurity Toolkit for Landscape Architects.

More about the LI CPD programme.

New tree planting: Selection, guidance, Autumn Budget bonus and management

New, informative and well-researched tree species selection resources are freely available. Each has a slightly different focus and aim.

Where are similar guides for herbaceous perennials, shrubs, grasses and geophytes?

Carbon storage – Quality over quantity

From Alternatives Journal: The importance of establishing species diversity in new tree planting schemes is that it increases carbon sequestration. Quality in selection, not quantity, is what’s important.

Houses of Parliament, Westminster


The 2018 Autumn Budget allows for £10m of funding between 2019-20 and 2022-23 for local community street trees and urban trees. (This is estimated to represent 100,000 trees, but there is no mention about money for maintenance of these trees.) In addition, a newly established Woodland Carbon Guarantee Scheme will support the planting of around 10 million woodland trees by purchasing up to £50m of carbon credits for qualifying tree planting.

But England’s tree planting record is lagging behind other EU countries, with 10% woodland coverage (in comparison with 30%+ in Germany, France and Italy). More significantly, over the next five years it is likely that England will suffer a net loss of trees through ash dieback.

Managing woods usefully

Telford, the ‘Forest City’, is so named by the former Development Corporation that planted over 15 million trees and saplings as part of the early landscape for the new town. The trees are part of the borough’s green heritage, but taking care of them is a mammoth job.

A new social enterprise, which is the vision of charity Small Woods working with Telford & Wrekin Council, will help to look after some of the 500 hectares of council-owned woodlands and use them as venues for social, craft and training activities that boost people’s confidence and wellbeing.

Professor Alan Simson ran the Afforestation Programme at Telford for over 10 years.

‘[I was involved in] planting something like 7 million trees of 138 different species,’ Alan said. ‘That work was partially responsible for colleagues from Scandinavia and Italy inviting me to help write the first European COST Action on Urban Forestry – COST E12 – which ran from 1997-2002 and established urban forestry in Europe as a specific scientific domain.’

What a fantastic legacy for the 50th anniversary of Telford New Town!

How could a ‘no-deal’ Brexit affect the plant trade?

The UK government has published a Brexit ‘no deal’ guidance note concerning importing and exporting plants and plant products. The LI Plant Health and Biosecurity Group responded, issuing a comment to LI members in a recent Vista newsletter.

Climate change, tree and plant health, and resilience

Forestry climate change

Climate change is threatening the health of trees and woods. A coordinated response is necessary to help them adapt and become resilient to current and projected effects.

As highlighted at the recent APF show, a significant group of public and private organisations have identified 13 priority actions – covering policy, research and practice – and pledged to work together on them over the next five years. The Action plan for climate change adaptation of forests, woods and trees in England, recently published by the Forestry Climate Change Working Group (FCCWG), represents the 35 organisations who signed a Forestry Climate Change Accord in 2015.

Other updates

Pests, diseases and management

Oak processionary moth

New legislation was introduced in August to protect oaks in protected zones against the risk of introducing oak processionary moth through import and movement. The legislation prohibits the movement of oak into the protected zones unless specific conditions are met.

New size restrictions on imported oaks are now enforced.

Forestry Commission Oak Processionary Moth Control Programme Evaluation (October 2018, London) – Findings

  • 2018 was a good year for the oak processionary moth. Larvae emerged late and developed quickly, meaning there was a very short window for pesticide application. A greater density of nests was recorded in infestation areas, with pheromone trap numbers also significantly higher. There has been no significant change in distribution of OPM this year – but we can probably expect an expansion next year.
  • Forestry Commission no longer fund nest control. (It is an inefficient method of population control and is detrimental to an OPM parasitoid which overwinter in nests.) The cost of managing public risk from OPM has been deferred to the LO and should only be carried out when there is a risk to people or domestic animals. Forestry Commission will continue to spray larvae in 2019 (only affecting early instars).
  • Heavy pruning/pollarding has reduced risk of re-infestation – although social research showed little public support for the approach.
  • Low levels of defoliation have been observed in year 1 of a 5-year study to assess long-term impact of OPM on oak tree health.
  • There have been reports of two horses, one dog and one cat affected by OPM.

Xylella fastidiosa

New import restrictions on Olive trees come into force on 26 November 2018. From this date, importers of olive trees must notify the Animal and Plant Health Agency (APHA). The statutory notification scheme for imports of certain plant and tree species from other EU member states will be extended on 26 November 2018 to include Olea europaea (common olive), in order to provide additional protection against the introduction of Xylella fastidiosa which was recently found in Belgium.

Read more here.

An ash tree

Ash dieback (Hymenoscyphus fraxineus)

In light of ash dieback, Forestry Commission has published new guidance on managing ash in woodlands. To follow in 2019 is  guidance on managing ash in non-woodland situations.

New safety guidance for felling dead ash trees has also been published in response to increasing incidences of accidents / near misses from chainsaw felling dead and diseased ash.

  • Ash dieback has been observed to progress more rapidly in woodlands with a high level of public access.
  • Canopy cover is not a reliable indicator of tree condition in mature ash – timber degradation and co-infected basal lesions in trees with low level of canopy loss (increasing chainsaw felling risk).
  • Diversity is critical to resilience of woodlands against disease, climate change etc. (Is there a case for including non-natives in new woodland planting?)
  • In a screening trial, ash originating from South East England (seed zone 405) is most susceptible to ash dieback (<1% of young trees healthy after 5 years). Scottish ash was least susceptible (2% healthy).

“Most people wouldn’t know an ash tree if it fell on their heads… better prepare yourselves”

Jack Dee

See latest news, events, projects and artworks from the Ash Project.

Abhainn Ashik to Yr Onnen by Ackroyd & Harvey. Photo: Gorm Ashurst. Source: The Ash Project


Keep an eye out…

Elm zigzag sawfly

First recorded in Europe in 2003, the Elm zigzag sawfly has spread and was identified in Britain in 2017. The species specialises in elms (Ulmus spp.) and appears to feed on all three elms commonly found in Britain.  Larvae feed on the elm leaf tissues, producing the characteristic ‘zigzag’ pattern of feeding damage.

The pest was first identified in Surrey in 2017. But in June this year, further reports came in from across a wide area of South East England and the East Midlands.

Oak lace bug (Corythucha arcuate)

Waiting in the wings? A native of North America, oak lace bug has been in Europe since at least 2000 – but so far, not in the UK. Initially reported in northern Italy, it is now found in at least 11 countries in continental Europe. It is a pest of Quercus (oak), but can also feed on a range of other broad-leaved trees. The pest feeds on leaves, and large populations can cause severe yellowing, then browning of the foliage and premature leaf drop.

More information at the Defra Plant Health Portal.

Defra Risk Register

5 more tree pests were added to Defra Risk Register in November 2018.

Online learning

Introduction to the UK Plant Health Risk Register

Presentation by Helen Anderson, Pest Risk Analyst at Defra. (PDF, 1 MB.)

Biosecurity learning online

The Forestry Commission, with input from the Animal and Plant Health Agency (APHA), the Arboriculture Association and the British Association for Landscape Industries (BALI), has developed a free e-learning package of 4 15-minute modules. The training outlines the main tree pests and diseases (current and potential), and provides clear guidance on the most effective and appropriate biosecurity measures to use in different situations.

Visit the Forestry Commission at their new website.

Out of the Woodwork

A blog led by Forestry Commission England’s Tree Health Team that provides a good basic introduction – perhaps a useful resource for clients?

Use of woods and trees

A corner of the old North Wood at Streatham Common is being used part time as a forest school, and you can see and hear the children and parents’ growing understanding and excitement of this environment. Not in 20 years has there been so many children’s voices in this wood. But landowners at Toys Hill are less in favour of starting young.

Engagement: Five great autumn activities to try with kids in the forest

Becky Wilkinson is the Royal Forestry Society’s Staffordshire Education and Teacher Training Officer. She outlines five great Autumn activities Primary teachers can try in the woods in this recent RFS blog.

Conferences (past and future) and other resources

  • The Tree Council, an umbrella organisation of which the LI is a member, has held two conferences this summer on urban forestry – specifically with the intention of getting the Tree Warden network up and running again. They have also been in discussion with the Department for Transport and the Chair of the Ministerial Review of Network Rail on management of railway land. More at
  • The Urbaner Wald (Urban Forest) symposium (Leipzig, October 2018) looked at the amount of ‘fallow’ land that is growing in cities, particularly in Eastern Europe. In the eyes of some of the city population, such land is a negative part of the urban structure. But adopting an urban forestry approach to the issue has great potential for biodiversity, climate protection, air pollution control, recreation, human health and wellbeing, and urban ecological renewal. Two days were spent discussing this quite creatively, and Professor Alan Simson was invited to give a keynote presentation on the benefits of an urban forestry approach. (If there are any English-translated proceedings we will post them in the next newsletter.)
  • The First World Forum on Urban Forests, Changing the Nature of Cities (Mantova, Italy, 28 November – 1 December 2018), looked at the changing nature of cities – past, present and future. A report on this event will follow in the next LI Plant Health and Biosecurity newsletter.
  • Unicef’s Shaping Urbanisation for Children: A handbook on responsive urban planning (2018) covers a lot of ground, but the section on playgrounds, squares and parks is particularly relevant to our work. (N.B. The link in this document to FAO’s online publications on urban and peri-urban forestry is broken; the correct link is here.)
  • Tree and Design Action Group (TDAG) sign up for events, meetings, newsletters and meeting minutes at
  • Green Connections: Empowerment through collaboration, Palmstead’s annual
    workshop, takes place at the Ashford Hotel on 23 January 2019. For bookings, see