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Posts tagged ‘Chalara fraxinea’

Woodland biosecurity – a simple guide

November 11, 2012

Gabriel Hemery

Brushing boots to disinfect and sterilise

Biosecurity – preventing the introduction and spread of harmful organisms – is big news at long last! The arrival of Chalara fraxinea in Britain has brought this important issue to the fore. However, I found it difficult to find simple guidance on the steps we should take when visiting or working in woodlands, or with individual trees in our trees and cities. Many of the record number of readers of this blog over the last week have found it after using searches such as:

“what should I do if I find Chalara fraxinea?”
“how do I clean my boots?”

While we wait for more detailed specific advice to come from scientists and Government officials in relation to Chalara fraxinea it would be prudent to follow the protocols developed to minimise the spread of another pathogen; Phytophthora. So my first recommendation is to visit the Forestry Commission’s webpage on Biosecurity Measures, which includes the advice currently given to all Forestry Commission staff for their routine visits to woodlands in a handy pdf guide.

I have put together the following simple guide on woodland biosecurity.

Biosecurity behaviour

Brushing boots to disinfect and sterilise

Brushing boots to disinfect and sterilise

  • Clean your footwear after visiting a woodland. Wear Wellington boots, as these are easier to clean thoroughly. To do this effectively you must remove first all soil and leaf litter from your soles. You will need water and a stiff hand brush.
  • If you have been to a high risk site apply a detergent to sterilise them, although it is good practice after all visits.
  • Sterilise your tools. Be careful that the chemicals you use do not harm trees (or other wildlife). Read more about sterilising forestry and woodland tools.
  • If you drive into a woodland, even on a road, wash your tyres to remove soil and leaf litter.

Biosecurity personal kit

Spraying boots to sterilise with Propeller disinfectant

Spraying boots to sterilise with Propeller disinfectant, after they have been brushed to remove soil

The most common question I’m asked is what chemical should I use to sterilise or disinfect. The one recommended, or at least adopted, by the Forestry Commission currently is Propellar™. This is available only directly from one supplier (see below) and must be ordered wholesale in 12×1ltr containers as a minimum order. I was amazed when I searched the websites of two of the major forestry and arboricultural supply companies that neither had any disinfection chemicals listed. This is really shocking! Try it yourself. Go to and enter a search string that allows you to search within a certain website (you will need to know the url of the forestry/arb supplier): try “ disinfectant sterilise” [replace the url with the supplier’s]. I’d be happy to be proven wrong but I’ve not found one yet that came up with any goods.

  • Propellar spray to sterilise forestry equipment

    Propellar spray to sterilise forestry equipment

    Propellar™ – chemical to sterilise footwear and equipment (always read the Health & Safety label). The supplier for the disinfectant Propellar™ is:

    Evans Chemical Supplies,
    18B Barncoose Industrial Estate
    TR15 3RX.
    Tel. 01209 213643
    Email: Evans Chemicals

  • handbrush – to remove soil from boots
  • disposable gloves – protection from chemicals used
  • safety goggles – protection from chemicals used
  • water container (e.g. 5L for personal/15L for groups) – to carry water in vehicle for cleaning after visit
  • airtight storage container – to hold brush and chemicals
  • soap and towels – to wash hands
  • bags – to dispose of material
  • storage box – to hold all biosecurity items together

If you have advice born from experience or other comments then I would be pleased to hear from you. Use the Comment box then you can share your experiences with other readers.

Finally, this advice can be followed by woodland owners, arboriculturists, foresters and anyone who accesses woodland regularly. Whether it is practicable or feasible for the average member of the public to adopt these measures is doubtful. Nonetheless, we can lead by example and on high risk sites or those with special high value (e.g. ancient trees or important habitats) particularly, it may be possible to erect signage or equipment to encourage visitors to undertake simple biosecurity measures.

Gabriel Hemery

Further Information

Ash chapter must now be rewritten

November 10, 2012

Gabriel Hemery

Ash (Fraxinus excelsior) shoot with emerging leaves. Drawing by Sarah Simblet.

Following the devastating news that the fungal pathogen Chalara fraxinea is rampant in the British countryside, our ash chapter requires now a major rewrite.

We had completed the section on ash (Fraxinus excelsior and other ash species) just one month ago, and had included a significant section on the potential dangers from this disease which was looming in continental Europe, little-knowing that within one month hundreds of British woodlands would be discovered to have trees infected with ash dieback.

Ash (Fraxinus excelsior) shoot with emerging leaves. Drawing by Sarah Simblet.

Ash (Fraxinus excelsior) shoot with emerging leaves. Drawing by Sarah Simblet for The New Sylva.

We have now just a few months of writing and drawing remaining before the book is put together by publishers Bloomsbury. Let’s hope that the news does not get much worse for this beautiful and graceful tree species before we go to press in late 2013.

Read more about Chalara fraxinea

Chalara fraxinea has been wild in Britain for at least two years

Lesion on young ash stem caused by Chalara fraxinea

After probably the largest-ever rapid survey of Britain’s woodlands, new incidences of Chalara fraxinea, the fungal pathogen that causes ash dieback, have been found in a possible 100 sites across the East and South of England.

After the announcement last week that Chalara fraxinea was in the ‘wild’ in the countryside of East Anglia in England, Forestry Commission staff have undertaken an unprecedented rapid survey. Every 10km square in Britain where ash trees were likely to be found was targeted, selecting four sites in each sampled square. The news is not good, as I predicted (see post).

Chalara fraxinea is present possibly in at least 100 sites, rather than the two where it was originally reported just one week ago. In addition to new confirmed sightings in Kent, possible occurrences extend to the Midlands and even Wales (see Forestry Commission latest map). Note that these are still to be confirmed officially but samples collected from many seem indisputable, even without any scientific analysis.

Today I visited Wayland Wood in south Norfolk as part of a specialist task force convened by Government. We viewed an area where hundreds of coppice stools of ash had succumbed to dieback (see pictures below).

Observing the branches of one more mature tree (with a stem about 30cm dbh) it was clear that this tree had suffered dieback during Summer 2011. This means that the Chalara fraxinea was present in Britain at least one whole year before realised, as indicated from tree physiology alone. When accounting for the life-cycle of Chalara fraxinea, then it is more likely that it was present from Summer 2010 if not even earlier. It is clear that the pathogen arrived in Britain by stealth before anybody recognised it.

Click to enlarge images

A stakeholder meeting is to be held on London today, and more details will emerge about the sightings that I report here. Scientists are working around the clock to confirm observations made in the field, by using sophisticated DNA sampling techniques on collected samples. Further expert groups are being set up and all concerned are working hard to provide practical advice to foresters, arboriculturists, nurseries and others.

Gabriel Hemery

Further information:

A ten-point plan for ash dieback Chalara fraxinea in Britain

Looming treescape

There has been too much knee-jerk reactionary panic to the arrival of ash dieback Chalara fraxinea to Britain’s shores, and a tedious jostling for position and profile between NGOs and others that supposedly put our trees first. Just days before it became a reality I wrote about the inevitable spread on ash dieback beyond the initial sightings in tree nurseries (read more), and subsequently about its likely impact (read more). The news about the disease has since become a very major story in Britain’s media and a widespread topic in daily conversation.

Looming treescape

Planning for a positive future for Britain’s trees and forests

Here is my proposed ten-point plan, in which some actions may surprise some.

  1. Do not fell mature ash trees in diseased areas.
  2. Lift the indiscriminate import ban on ash trees.
  3. Increase urgently funding for genetic research into resistance to ash dieback.
  4. Support research into understanding the pathogenic fungus Chalara fraxinea.
  5. Provide silvicultural practice guidelines in dealing with ash dieback.
  6. Initiate public education about tree health and biosecurity.
  7. Support citizen science initiatives that enable monitoring of tree health (e.g. TreeWatch)
  8. Provide funding sufficient to implement the Forestry Commission Tree Health Strategy (see below).
  9. Bolster Forest Research science funding into tree health.
  10. Stop blaming the Government for ash dieback.

1. Do not fell mature ash trees in diseased areas

Killing trees in areas around diseased trees could wipe out any of nature’s in-built resistance to Chalara fraxinea. It is clear from continental Europe that up to one-third of ash trees exhibit some resistance to ash dieback. Ash is a very genetically diverse tree species, unlike elm (which is why that species was devastated by Dutch elm disease), so we must give nature a change to display this resistance. Mature and resistance ash trees should be allowed to stand, allowed or encouraged (via tree breeding scientists if necessary) to interbreed and to produce our next generation of healthy ash trees.

Those trees that do succumb will provide fantastic deadwood habitat if allowed to remain standing (when safe to do so), or can be felled when convenient to provide highly-valuable timber when the market demands it, rather than the market being flooded due to mass-felling and the inevitable price crash.

2. Lift the indiscriminate import ban on ash trees

The phrase “shutting the stable door after the horse has bolted” comes to mind. The presence of ash dieback in our nurseries was known about since February. We may have been able to have prevent this had the ban been in place before 2012. Now, it is too late, and pointless given that the disease is loose in the ‘wild’. The disease will spread without much influence from an ash import ban, or even a moratorium on planting ash, which will only, at best, slow its distribution.

It is quite likely that the occurrences in the East of England arose by other means rather than on young plants. It can be spread by water droplets, bird’s feet, forestry and tree machinery, footwear, dog’s feet, car tyres and by wind. Its arrival in Britain was inevitable. Instead of a blanket ban I would like to see a selective control on young trees imported; allowing in only those that have shown some resistance to the disease.

3. Increase urgently funding for genetic research into resistance to ash dieback

We should increase collaboration with international scientists. Some involvement with the Fraxback programme (see below) exists and should be built upon. Work by the Future Trees Trust on selective breeding on ash should be supported further; specifically to enable disease resistance trials to take place, ideally jointly with other European partners.

4. Support research into understanding the pathogenic fungus Chalara fraxinea

As in 3., increase collaboration with international scientists, and recognise that increased funding may be necessary.

5. Provide silvicultural practice guidelines in dealing with ash dieback

We must build on the excellent work done in continental Europe where there exists over a decade of experience in dealing with the pathogen to provide straightforward silvicultural guidelines to forestry practioners (e.g. Thomsen and Skovsgaard 2012). We need some clear guidelines both for foresters and arboriculturists in how best to deal with the disease and with diseased trees.

6. Initiate public education about tree health and biosecurity

There exists widespread ignorance about tree health and biosecurity among the public, and a lack of knowledge by decision makers concerning the capacity of the public to respond positively to increasing biosecurity measures in the countryside. Research is required to tackle the latter, and a more co-ordinated response required by the sector to tackle the former; leaving any chest-beating and self-promotion behind.

7. Support citizen science initiatives that enable monitoring of tree health

The age of the citizen scientist is upon us. There are a number of schemes and initiatives running currently that provide the wherewithal for members of the public to take an active part in monitoring tree health across the country. While recognising the irreplacability of the trained scientist, we must also recognise the increasing strains placed upon our beleagured tree scientists from ever-decreasing funding (and therefore manpower) coupled with ever-increasing tree health issues. Some examples of citizen science initiatives include Ashtag which has been set up to monitor ash dieback, and the broader tree health initiative TreeWatch – Adopt an Ash.

8. Provide funding sufficient to implement the Forestry Commission Tree Health Strategy

The Forestry Commission has developed an excellent Tree Health Strategy. This now needs to acted upon urgently and funding provided sufficient to ensure that Britain’s trees and forests are protected and enhanced into the future. See link below.

9. Bolster Forest Research science funding into tree health

During 2012 alone tree scientists at Forest Research have had to face an Asian longhorn beetle outbreak, sweet chestnut blight, and ash dieback. This is in addition to oak processionary moth, Phytophthora ramorum in Larch, and acute oak decline that were already big-enough problems to tackle. It is important to recognise that it is not just the science work itself that is stretched, when delivered by an already small team, but that every new disease or pest demands time. Time in dealing with the media, with politicians needing briefing, from concerned and well-meaning members of the public and organisations. Every meeting attended and briefing note produced is less time spent on finding out more about the problem and how it can be tackled. Every budget cut stretches further their capacity to deliver and demands more time spent away from the science trying to raise external funding.

The team of scientists at Forest Research are an amazing resource but anyone who is lucky enough to deal with them will know that they face an impossible task, even before “the biggest story since Dutch elm disease” entered their work stream. They need more funding so that their team can be expanded and better resourced. A key objective from the Tree Health Strategy (see 8.) is “secure sufficient resources to ensure that biosecurity is not compromised.

10. Stop blaming the Government for ash dieback

Nothing will stop the spread of ash dieback across Britain, and given its relentless spread from Eastern Europe over the past 20 years, its arrival on our shores was inevitable. The current actions led by Defra will, at best, only slow its spread. Pretending that ash dieback in Britain is the fault of Government is simply shallow chest-beating, and everyone knows it. Let’s get on with the actions above by working together for the good of our trees and forests.

Gabriel Hemery

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Ash dieback spreads in British countryside

October 25, 2012

Gabriel Hemery

Chalara fraxinea ash dieback distribution map in Britain

Ash dieback caused by the pathogenic fungus Chalara fraxinea has been confirmed on woodland trees in the British countryside.

In this case I am not happy in being proven correct in my prediction of just two days ago, see Ash dieback could devastate Britain’s landscape, that the disease was in all likelihood already loose way beyond the tree nurseries where it was first reported. As Britain’s third most common tree species, the consequences are indeed very serious.

The outbreak in East Anglia was confirmed today by plant scientists from the Food and Environment Research Agency (Fera). Ash dieback Chalara fraxinea was found at two separate sites: (1) the Woodland Trust’s Pound Farm woodland in Suffolk, and (2) Norfolk Wildlife Trust’s Lower Wood nature reserve near Ashwellthorpe. These are the first confirmed reports following the initial import of the disease on plants brought in from the continent by a Buckinghamshire nursery, which subsequently distributed ash plants to some 90 customers across the country. The location of these initial plantings is not public knowledge.

Download the latest national map of confirmed Chalara outbreak sites

Download the latest national map of confirmed Chalara outbreak sites from the Forestry Commission

[UPDATE] I prepared initially my own Google map to mark these first countryside outbreaks. The Forestry Commission have subsequently been releasing a national map of confirmed outbreak sites on a regular basis, so instead I now provide a link to their online map here (it is quite a large pdf file so allow some time for it to download).

Gabriel Hemery

Read more:

Ash dieback could devastate Britain’s landscape

Ash in Britain

Name an iconic tree species for Britain … Did you answer oak or Scots pine? My guess is that it was one or the other. There is another species however that holds a unique place in British landscapes, not just in lowland forests, but in our uplands, in wet woodlands, among hedgerows and fields, in streets, parks and gardens – the ash Fraxinus excelsior. It may not demand our attention in the same way as some other tree species but it is extremely valuable and important in so many ways.

Ash trees at dawn in Cumbria

Ash trees at dawn in Cumbria. Photo

Ash in Britain

Ash (Fraxinus excelsior) in Britain and Ireland from The New Atlas of the British and Irish Flora, Oxford University Press. Click to view an online version from the BSBI website.

Take a look at the distribution map (right) for ash – every blue dot represents a 10×10km square in Britain where ash is present. Very few places in Britain are without ash trees. It is a vital component in the ecosystems of many mixed woodlands, being an ideal companion to oak and other hardwoods. It regenerates readily being adapted perfectly to the British climate. Its wood remains one of the best materials for sporting goods, makes beautiful furniture, while its properties for firewood are unrivaled.

Imagine therefore a scenario where ash may disappear from our landscapes. Horrifying – yes; a reality – quite possibly.

Readers may have picked up the worrying news that during an official inspection carried out in February 2012, symptoms of ash dieback were observed on Fraxinus excelsior in a nursery located in southern England. Suspect symptoms were identified in a batch of 600 plants which had been imported from the Netherlands in November 2011. The presence of Chalara fraxinea (EPPO Alert List) was confirmed on the basis of the morphological characteristics of the pathogenic fungus. Eradication measures were put immediately into place and the infected lot of F. excelsior was destroyed. Further investigations on the site revealed suspect symptoms in other Fraxinus species which had also been introduced into the nursery in November 2011. Investigations have been carried out to trace-back all Fraxinus consignments originating from the same Dutch supplier which had been imported into the United Kingdom, as well as to trace-forward all plants from the infected lot which have already been sold by the British nursery.

In Denmark, around 90% of all ash trees have been affected by Chalara fraxinea, and it is rampant across northern and central Europe. Young ash trees are particularly vulnerable and can die within one year, while older trees although capable initially of surviving the dieback, are likely to die after two or three consecutive years of infection.

According to the official line (see links below) the fungal disease has not yet been found in the natural or wider environment in Great Britain, that is, outside nurseries and recent plantings. My guess is though that it is already loose and rampant in our landscape. History tells us that we usually become aware of serious pests and pathogens late in the day. Pests and diseases can appear and then take time to impact too. For instance, Dutch elm disease was first detected in Britain in 1927, and was probably present before then, yet it was not until the 1960s that millions of elm trees were affected by the disease and mature elm trees wiped from our landscape.

Chalara fraxinea is being treated as a quarantine disease under national emergency measures, and it is important that suspected cases of the disease are reported. See the links below to aid in identification.

More about Tree Health

Further information:

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