The Xylella x fastidiosa Biosecurity Crisis.

What is Biosecurity?

Biosecurity  Definition

the methods that are used to stop a disease or infection from spreading from one person, animal, or place to others:

Chicken farmers have strengthened biosecurity to prevent contamination from people who have visited live-bird markets.

Majestic Trees has been calling for much tighter controls on the movement of trees across Europe and into the UK since our first open letter to industry (one of many) in May 2013. Subsequently, our MD has been very active in the industry debate because of the avalanche of new pest and diseases that have hit Europe over the past 10 years. He has spoken at a number of events about the need for change, though in the early days days his concerns often fell on deaf ears.  With the unfolding crisis surrounding Xylella x fastidiosa, however, times are changing and a rapidly growing number are now joining the voices for change. Those voices include His Royal Highness The Prince of Wales, who on 1 February 2018 called a Biosecurity Conference at Highgrove, inviting key nurserymen from the UK and mainland Europe, along with important industry stakeholders and policymakers, to discuss the issue as a matter of urgency. 

Change could be dramatic.  For example, Hillier’s have called for a complete ban on plant movements and Barcham’s are proposing a complete ban on rootballs going direct to site from Europe.  These proposals may, at face value, seem unrealistically drastic, but both would indisputably reduce pest and disease movement and are more realistic propects post Brexit, especially in context of the seriousness of the threat.  HRH The Prince of Wales articulated the gravity of the situation very well at the Highgrove conference, posing the question “when the stakes are so high how can we say it is too much to ask?”, going on to say that “the future without trees is unthinkable, and to contemplate this demands a national emergency”.  With statements like “we must find a solution before it is too late” and “if we fail to act we will be showing our arrogance towards nature”, it was a very passionate speech indeed, especially when HRH recounted his personal experience of first felling 160 Elms at Highgrove 38 years ago, but now in the past 10 he has been felling Ash, Oaks, Aesculus, Castanea and what next?  His sentiment was certainly one of action, not discussion, and I think we all sensed that this sentiment was shared by Michael Gove, the Minister responsible for DEFRA.

One could spend a lot of time explaining the complexities of the issue, but the central problem is that there is a staggering amount of plant material circulating around Europe, much of which is passing through Holland from the south of Italy, where Xylella has destroyed huge swaths of plant material.  Therefore it is absolutely vital that any of us in the industry sourcing plant material ask our plant suppliers EVERY TIME for proof of where the plants, trees, etc. being sourced have been growing over the last TWELVE months, and if this cannot be proved, REFUSE TO  BUY THEM.  With so many threats none can afford to be complacent, and not just in the interest of the greater good – imagine the liability to be faced by accidentally introducing Xylella into a project? Will the supplier you have sourced from stand behind their product when the general contractor sues?  These are not questions any of us want to be facing.

EU regulations state that should a confirmed case of Xylella be documented all infected plants must be destroyed along with every potential host plant (there are 70+ species which many think will eventually grow to 300) within 100 meters, followed by a quarantine on the area that will be enforced for 5 years.

This would take some explaining to a client, particularly if Defra’s best industry practice guidelines (see below) had not been followed in sourcing the plants.

A Quick Overview of the biosecurity threat from Xylella x fastidiosa

Xylella fastidiosa (X. fastidiosa) is a bacterium which attacks the water conducting systems of plants, restricting the movement of water and nutrients with often devastating and in many cases fatal consequences for the host plant.  It differs from most other known plant diseases in that it is known to attack a wide range of tree species, including many commercially grown plants such as grapevine, citrus, cherry and olive, and many tree species which exist widely in the natural and cultivated landscapes of the UK, including several species of oak, maples, and flowering cherries.  It also attacks many herbaceous and shrub species widely used in landscaping and garden design, including lavender, rosemary and salvia.


Although the disease has been a serious issue in the Americas and Taiwan for many years, it had never been found in Europe until 2013, when southern Italy experienced a sudden and widespread deterioration in trees across its olive tree plantations which was determined to be caused by infection with Xylella x fastidiosa.  Two years later the disease was detected in Corsica, and cases have since also been confirmed in Spain, mainland France and Germany.

Fortunately, there has been no detection of Xylella in the UK to date, however the risk of introduction is extremely high due to

  1. the significant importation of plants (£1.4 billion per year) to the UK from Europe.
  2. the prolific movement and exchange of plant material amongst growers and traders in Europe.
  3. the lack of any screening for this disease at UK borders due to the EU’s freedom of movement.
  4. the lack of robust protocols for monitoring and tracing chain of supply from the UK back to source.
  5. the increase in UK plant import traders/brokers and ‘Virtual Nurseries’ who have no licensed nursery premises, are not covered by an Nursery Stock Licence or have to worry about Plant Passports and instead import to order, arranging for delivery of plant material direct to the end user.
  6. the public being legally allowed to bring plant material back from anywhere in Europe, which nurserymen claim is a huge loophole and threat.

Defra (the Department of Fisheries and Rural Affairs) are moving as swiftly as possible under current EU legislation to address the threat and bolster import regulations and protocols, however many of these changes will take 2-3 years to fully implement. Due to the excellent science based evidence provided to the EU a lot of pZ zones have been agreed (plant-passports-protected-zones-0118.pdf), but with the Plant Passport system leaking like a sieve this does not guarantee much protection. Meanwhile, Defra is encouraging vigilance and adoption of ‘industry best practice’ guidelines (see below) within the UK horticultural industry, to include growers, garden centres and traders; garden designers, landscape architects and landscape contractors; arboriculturalists and tree surgeons; and professional bodies and organisations.  It is a call to action we are taking very seriously and we would urge our industry colleagues to be proactive too.

Recommended Industry Best Practice for Xylella vigilance

(extract from the Nov 2017 Defra document UK plant health guidance:  Xylella fastidiosa: Information about controls for importers and users of trees, shrubs and herbaceous plants.)
  • Ensure that plant passports arriving with host plants are correct and keep the plant passport to aid trace back if necessary. This may also support assurance schemes your business may be in.
  • Source from known suppliers or visit suppliers to view their processes, procedures, biosecurity arrangements and the plants they grow. Defra guidance on high risk hosts.
  • Make sure that imported plants both originate from and are sourced from disease free areas. Defra information on infected areas can be found here. 
  • Isolate or quarantine new batches of plants and monitor them during the growing season for signs of the disease – whilst not a legal requirement it is good practice to place ‘imported’ hosts of Xylella in a quarantine area – ideally a good distance away from other host plants and if possible place under physical protection. If any outbreak is confirmed all ‘host’ material within 100 m will need to be destroyed
  • For contractors/designers, ensure that plants you use have been ordered early and monitored for disease in a low risk area, before being planted at their final destination.
  • Label and keep records of the identity of all received batches of plants including: where the plants came from and when.
  • Maintain records of pesticide treatments.
  • Destroy old or unusable plants.
  • Comply with the UK national requirements to notify the UK Plant health Service about certain species of plants under the ‘EU Plant and Tree notification scheme’.

At Majestic Trees, we are proud to be able to say that our biosecurity practices far exceed the recommended industry best practice outlined by Defra above. We spend weeks every year personally tagging virtually every tree and hedging piece that we buy in for production stock. No other nursery in the UK invests the time we do in travelling, inspecting nurseries’ biosecurity regimes and growing practices, enquiring about stock providence and tagging the many 1000’s of trees we import in order to dramatically reduce any biosecurity risk to both Majestic Trees and to our customers. We are fanatical about our standards of quality and customer care. It is the secret of our success and reflected in our excellent track record for industry awards.

Useful Links:

Defra Xylella overview document(as cited above:  an excellent, succinct overview briefing for the industry).
Confirmed Hosts Plant List (Defra)
EU Affected Zones List

Defra updates:

Xylella x fastidiosa: latest information:
Xylella x fastidiosa:  EU controls:
Xylella fastidiosa:  UK secures added EU protections:
Issuing plant passports to trade plants in the EU.  (current requirements):

Xylella In The Press

UK gardens threatened by 'game changing' plant disease from Europe (Independent, Dec 29 2017)
Buy UK plants to avoid killer foreign bacteria, gardeners warned  (The Telegraph, 29 Dec 2017)
The Dangers of Xylella fastidiosa (The Telegraph, 23 Feb 2016)