Issue 8
November 2016

Welcome to the latest issue of Tree Health News.

Please do continue to share this resource via your social networks (using the buttons below), and remind your colleagues to sign up if they haven’t done so already.

Join the conversation by following us on Twitter.

News in brief

Join the Conversation: #KeepItClean Tweetchat

Have you ever wondered which disinfectant to include in your biosecurity kit? Or how Phythopthora ramorum can be spread between woodlands? Or how to spot chalara on your trees?

On Wednesday 30 November between 4 and 6pm Dr Kat Deeks and Mick Biddle from our Tree Health team, and Dougal Driver from Grown in Britain will be available on Twitter to answer any questions you may have about tree health and biosecurity.

Just follow #KeepItClean between 4-6pm on 30 November to take part.


Winter is coming… and with it increased sales of firewood. If you are buying firewood for the colder months ahead, look for the Grown in Britain logo which ensures the wood has been sustainably harvested and is legally grown within the UK.

Grown in Britain has a list of licensed suppliers on its website.

Canker stain of plane – booklet

The London Tree Officers Association (LTOA) and Treework Environmental Practice have published an English language second edition of the booklet Detecting and identifying canker stain of plane, written by Professor Lucio Montecchio. If you are interested in finding out more about this disease threatening London plane trees, you can request a copy of the booklet by contacting the LTOA.

In depth

New pest and disease web pages

We have published new web pages of information about more tree pests and diseases which are not believed to be present in the UK, but which have been identified by the Government’s Plant Health Risk Group as being at increasing risk of accidental introduction. As a result we have written contingency plans for each of them, setting out the actions that would be taken if they were discovered here.

The pests and diseases concerned are Pitch canker of pine, Siberian silk moth and Bronze birch borer.

In addition we have published contingency plans for outbreaks of Pine processionary moth, Pinewood nematode, Oak processionary moth, European spruce bark beetle (Ips typograhus), Sweet chestnut blight, Elm yellows phytoplasma, Plane tree wilt and Emerald ash borer on the existing web pages about these pests. Links to all of these pages about threats ‘on the horizon’ are available at

We encourage all Tree Health News readers to familiarise themselves with the information about these pests, and to remain vigilant for them and report any suspected sightings with Tree Alert.

Keep an eye out for Sirococcus blight

Readers are asked to watch for and report suspected cases of Sirococcus blight on cedar and hemlock trees after it was discovered recently for the first time in the UK.

Sirococcus blight is caused by a fungus called Sirococcus tsugae, which had previously been confirmed only in North America and Germany. It has now been confirmed at sites in England, Scotland and Wales.

Further information, including photographs of symptoms, is available on our website at, and the Forest Research website at Reports of suspected cases should be made with Tree Alert.

Dead Trees Don’t Please: handle young trees with care

It’s tree planting time, so it’s worth considering the importance of taking care of your young trees and planting them well. Some key things to remember include:

  • choosing tree species that will thrive at the destination site;
  • only buy plants from reputable nurseries that can provide documentation of seed source and growing history (Remember, many of our current diseases have arrived on imported plants.);
  • check your trees on arrival that they are the ordered species, correct size, with a good root system and in a healthy and fresh condition and record your inspection;
  • reject plants that appear in poor condition, dried out and of poor form and root structure, because unhealthy plants will not recover;
  • handle bags of plants with care: do not throw bags, and keep bags in the shade away from extremes of temperature;
  • do not plant into frozen, dry or waterlogged ground;
  • plant as soon as possible, planting sensitive species first; and
  • water if possible during periods of drought.

With sensitive handling and good planting, trees that arrive healthy from the nursery should thrive.

There is more information on planting and establishing woodlands available from the Forestry Commission England website.

Oak processionary moth (OPM)

The annual Oak processionary moth control operation in London, Surrey and Berkshire wound up in September. We are pleased to report another reduction in the number of nests found in the Bromley/Croydon outbreak area of South London, and for the fourth successive year no nests were found at Pangbourne, in West Berkshire. However, the capture of a small number of male adult moths in pheromone traps around Pangbourne suggests that a residual population of the pest persists in the area.

OPM nests were discovered for the first time in Hertfordshire (in the Watford area); in Buckinghamshire (close to the boundary between South Buckinghamshire and Hillingdon Borough); and in the Mole Valley District of Surrey.

We will soon be mounting our winter survey for nests, some of which are more easily discovered when the leaves are off the trees.

We are making plans for 2017 and will communicate them when the proposals and budget have been approved.

For further information visit or write to

Phytophthora ramorum update 2016

The 2016 Phytophthora ramorum aerial surveillance programme has been completed. The team overflew nearly 800,000 hectares of woodland, assessing more than 30,000ha of larch, and we continue to issue Statutory Plant Health Notices (SPHNs) to fell infected larch and other infected sporulating host trees.

Symptoms in larch have mostly been at a low level in the vicinity of previously confirmed infection (either in larch or rhododendron). They have comprised mainly small groups of trees or individuals, and have been as subtle as single crowns and branches. There was localised spread in a small number of cases where there was a concentration of sporulating hosts. The most extensive areas of larch infection were in Wiltshire, in association with previous infection.

We continued to see low-level collateral damage in species including beech, Douglas fir, noble fir and western hemlock at sites close to new larch infections, and at sites of previous larch infection which have been felled. Although these species are 'terminal' (non-sporulating) hosts, and therefore pose no risk of spreading the disease, their continuing death and dieback demonstrate P. ramorum’s potential to persist on sites where large amounts of inoculum have been generated. Our investigations suggest that it can remain viable and continue to cause expanding stem lesions in some terminal tree hosts for at least five years. It was also detected on bilberry and oak on a small number of larch infection sites.

Following the 2015 findings of sites with infected sweet chestnut in Devon and Cornwall, the team was especially vigilant for signs of further cases, and undertook two flights specifically surveying sweet chestnut. Suspected sites were followed up on the ground, and 30 were confirmed with P. ramorum infection. Most were in Devon and Cornwall, with some in Wiltshire, and SPHNs are being issued for all of them. Fourteen of the positive sites appear to be isolated from the immediate presence of other sporulating hosts, or previous infection, adding to the evidence that long-distance spread to sweet chestnut is possible. Forest Research continues to investigate this.

Andy Hall, our Tree Health Team leader, commented,

"Despite the weather during autumn and winter of 2015/16 having been ideal for disease spread, the continuing overall downward trend in the area of trees needing to be felled for P. ramorum control purposes indicates that our rapid-reaction strategy, and the more recent biosecurity campaign, is working to manage the levels of the disease. It is a tribute to the public-spirited co-operation of affected woodland owners who have had to sacrifice valuable trees before their time, and I thank them most sincerely for their support.”

And finally...

Choosing your Christmas tree is undoubtedly one of the highlights of the festive season, but other than size and variety, what should you consider when choosing your tree

As we know, tree pests and diseases can enter the country on imported plants and Christmas trees are no exception to this risk. Ensuring your Christmas tree has been biosecurely grown should be at the top of your checklist.

We grow approximately 10,000 Christmas trees every year from British seed and all trees grown on the Public Forest Estate are grown sustainably in accordance with the UK Woodland Assurance Standard (UKWAS).

And, this year when you buy your Christmas tree from Forestry Commission England, it will come with a free sapling, allowing you to plant and grow your own real Christmas tree for the future.

To find your nearest centre to buy your Christmas tree visit


Forestry Commission England Area tree health events

November 2016 – March 2017

We are once again delivering our series of local tree health events. These popular sessions run throughout the year and typically include speakers from the Forestry Commission, Forest Research, APHA and across industry. Topics often include local tree health updates, biosecurity, tree planting and resilience as well as updates on the latest guidance and legislation around tree health.
These events are often over-subscribed so if you are keen to find out more about your local events, contact your local Area team to check dates, locations and availability of places.

Innovation in plant biosecurity conference

15 & 16 March 2017

This major conference will bring together plant health professionals and invasive species experts from around the world to discuss novel strategies for improving plant biosecurity and establishing a sustainable knowledge exchange.
Early bird tickets are now on sale from the Fera website at the discounted price of £150, and need to be purchased by 30 November to qualify for the £50 discount.

Early Bird Booking Opens for Trees People and the Built Environment 3

5 & 6 April 2017

Early bird booking has opened for an acclaimed international urban tree research conference. Trees, People and the Built Environment 3 will return to Birmingham University, 5-6 April 2017.
This conference will focus on two significant areas of research – health and highways.
Early bird tickets are now on sale from the Institute of Chartered Foresters website.

For a wealth of tree health resources, visit
the Forestry Commission’s dedicated web pages.

If you have any questions please email us.

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