Issue 6
May 2016

Welcome to the latest issue of Tree Health News.

Thank you to those who participated in our recent online survey, and provided us with feedback about how you read and use the information in this newsletter. As a result, you’ll see that we’ve made some changes to its layout, which we hope will make it easier to read and navigate.

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News in brief

Keep it Clean: Don't Give Pests and Diseases an Easy Ride

What should a biosecurity kit include?

We have been adding to the resources available on our website since the launch of our biosecurity campaign aimed at tree professionals earlier this year.

We now have a page with up-to-date guidance on assembling your own biosecurity kit. Do keep checking the web pages as we add more information and guidance.

Follow @DrKatDeeksFC on Twitter for regular updates.

Increase Your Pest and Disease ID Knowledge

Free downloadable pest and disease guides now available.

Citizen science initiative Observatree has made its downloadable resources and videos available from its website to help you identify priority pests and diseases and spot early outbreaks. They include a pest and disease calendar so you can check at a glance for seasonal issues you should be aware of.

As ever, please report any indication of ill health in trees to us via Tree Alert.

Register to Vote

If you aren't already registered to vote you need to do so before 07 June to vote in the EU Referendum. Register to vote at

In depth

Oak Processionary Moth

The annual programme is under way to control the population, spread and impacts of oak processionary moth (OPM) larvae in London, Surrey and Berkshire.

OPM larvae (caterpillars) are a hazard to tree, human and animal health, and under our Defra-funded control programme we are treating affected trees with approved insecticide, to be followed in the summer by manual removal of nests and caterpillars.

Larvae which survive treatment will grow big enough and descend low enough in the trees to be seen and recognised by the untrained eye about the last week of May. About then they will also develop the hairs which can cause itchy skin rashes, eye irritations and, occasionally, sore throats and breathing difficulties in people and animals that come into contact with them.

Tree, landscape and ground-care professionals and others working near oak trees are therefore strongly advised to wear personal protective equipment and to familiarise themselves with the regulations applying to movements of oak material in the affected areas.

They are also ideally placed to supplement our formal surveying by reporting any OPM they see with Tree Alert.

Guidance on all aspects of OPM identification and management is available on our website, including an OPM manual and a toolkit of resources.

Keep it Clean: Biosecurity for Landscapers

Following the biosecurity guidance aimed at arborists and foresters which we launched earlier this year, we now also have tailored guidance available for landscapers.

It encourages landscapers to ‘think kit, think plants, think materials’ and has been developed by the Forestry Commission and APHA, in partnership with BALI, HTA and the Landscape Institute.

The guidance is available to view on our website.

We’re all responsible for biosecurity. Pests and diseases can be harboured in live trees and plants, in organic material and on machinery and tools. Tree and plant professionals are at higher risk than most people of spreading pests and diseases because they often work across multiple sites, transporting plants, kit and machinery with them.

Landscapers, like arborists, foresters and other tree professionals are in an ideal position to spot and report symptoms of pests and disease early. And, by taking action promptly, we have a better chance of eradicating or containing outbreaks or minimising their impacts.

P. Ramorum on Sweet Chestnut

We are continuing to investigate cases of Ramorum disease in sweet chestnut trees (Castanea sativa) in South-West England, mostly in Devon and Cornwall.

Unlike previous cases of the disease in sweet chestnut, these trees are not standing close to infected plants of other species such as rhododendron or larch.

Please therefore keep an eye out for signs of ill health in sweet chestnut trees now that they are in leaf again, and report suspected cases to us using Tree Alert. The symptoms are crown deterioration, foliage dieback, wilting and discoloured leaves, premature leaf fall (i.e. before autumn), and characteristic bushy, epicormic growth at the bases of affected trees.

We are working with Forest Research to understand the disease and its impact on sweet chestnut so that we can provide the best possible advice for growers and owners, and devise appropriate control measures. The numbers of trees affected are relatively small.

We have published a guide to symptoms and will add to this information as our knowledge of the condition develops.

Oriental Chestnut Gall Wasp (OCGW) Surveillance   

We will be surveying sweet chestnut trees again this summer for any further signs of OCGW in the wake of last year’s discovery of outbreaks in Farningham Woods, near Sevenoaks in Kent, and in St Albans in Hertfordshire.

As well as surveying in and around the outbreak areas, a sample survey of chestnut trees in high-risk areas will be carried out across South-East England and East Anglia.

We ask anyone who owns or lives, works or recreates near sweet chestnut trees to keep an eye out for the tell-tale galls, or growths, which indicate the pest’s presence, and report sightings to us without delay with Tree Alert. Identification guidance is available on our website.

Forest Research Calls For Nursery Partners to Help Tackle Phytophthora

Forest Research is inviting nursery managers and other plant traders to take part in scientific research into Phytophthora infections in the trade.

The project complements our ‘Keep it Clean’ campaign to promote good biosecurity practice at work to minimise the spread of plant pests and diseases.
Dr Sarah Green, senior forest pathologist at Forest Research, explained,
“As people in the trade are well aware, our plant trade and natural environments are being affected by a range of destructive Phytophthora organisms which have entered Britain from different parts of the world. They arrive and are spread around the country in soil, water, equipment and in the tissues of a large number of plant species, damaging business and ecosystems alike.
“We are looking for plant nurseries and traders to take part in this project to enable us to better understand the dynamics of Phytophthora spread and infection, and devise effective control measures. They can do this by sharing their expertise and experiences with us, and allowing us to sample water and plants at regular intervals during the project.
“In return, we will provide them with information about their Phytophthora risk, and work with them to reduce it. Ultimately the project will provide invaluable data which will help businesses to effectively manage their risk.”
All published data on nursery findings will be anonymous, and it will not be possible to identify any individual businesses from the published findings.
Anyone interested in an informal discussion about ways to get involved may email Dr Green. Further information about the Phyto-Threats Project is available on the Forest Research website.

Betty the Tolerant Ash Tree

In case you hadn’t seen the news, there’s been a breakthrough in dealing with Chalara ash dieback.

UK scientists have for the first time identified an ash tree that shows clear tolerance of the fungus which causes the disease, raising the possibility of breeding tolerant trees it.

Chalara Ash dieback is now found in most parts of the UK, and a great number of trees are infected in one woodland in Norfolk. However, some of the trees in the woodland appeared to have very low levels of infection, and researchers identified one of them, which they nicknamed ‘Betty’, as having a strong tolerance of the disease.

The team compared the genetics of trees with different levels of tolerance. From there, they identified three genetic markers which enabled them to predict whether a tree is likely to be tolerant – even whether it is likely to be ‘mildly’ or ‘strongly’ tolerant. Betty, they discovered, was predicted to show strong tolerance.

The findings were announced in April during a visit to the John Innes Centre in Norfolk by Defra Minister Lord Gardiner and Professor Nicola Spence, the Chief Plant Health Officer.

For Forestry Commission guidance and information on Chalara, visit our website.




15, 16, 17 September 2016, Ragley Estate, Warwickshire

Advance ticket sales are now open for APF 2016 – the largest forestry, woodland, arboricultural, trees and timber event of the year. The event will showcase the newest state-of-the-art machinery available, reflecting everything that happens in the modern working woodland and tree industries.

Advance tickets - £18 (discounts available for groups). For information and tickets visit

And remember, if you are going to APF, arrive clean. Scrape, brush or knock soil from your boots and clothing before arriving on site.

And finally...

Criminal: Perfect Specimen

Tree health is the subject of a podcast that forms part of the popular American series ‘Criminal’ which sets out to explore complex and sometimes unsolved crimes.

This particular story looks at the mystery surrounding the 500-year-old Treaty Oak in Austin, Texas, when the city forester started to wonder whether someone intentionally tried to kill it. 

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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