Tree pests and diseases are a bigger threat than ever, says Keith Sacre, but it’s up to you to make the difference
There are some words written in the first draft of BS 8545 Trees: From Nursery to Independence in the Landscape, which went out to consultation in late 2013, which did not appear in the standard when it was published in 2014:
‘Bio-security is an important consideration. To minimise the risk of pests and or diseases being imported directly into the UK, all young trees produced abroad but purchased for transplanting should spend at least one full growing season on a UK nursery and be subjected to a full pest and disease control programme.
Evidence of this control programme, together with a comprehensive audit trail of when imported trees were received and how long they have been on the nursery, should be obtained from the supplying nursery. The audit trail should extend beyond the nursery after dispatch, allowing for full recall in the event that any pest and/or disease problems manifest themselves in the landscape.’
These paragraphs did not make it into the published document because no new standard published in the EU could be seen to inhibit free trade. Yet the problems associated with imported pest and diseases has, if anything, grown since the above was written. The influx of imported pests and diseases in recent years is well documented, and continues to be so.
The list seems sometimes to be endless, with fresh threats such as Emerald Ash Borer, Asian Long Horned Beetle, Pine Wood Nematode, Eight-Toothed European Spruce Bark Beetle, Citrus Longhorn Beetle and Bronze Birch Borer all listed on the Forestry Commission website as pests yet to arrive in the UK. Plane wilt (Ceratocystis fimbriata x plantini) is hovering in France, presenting a huge potential threat to London Plane, and the recent publicity surrounding the threat of the bacterium Xylella fastidiosa to olives and other fruit in southern Europe has highlighted another potential threat with a huge range of susceptible trees.
There seems to be a clamour for action by well-meaning politicians, usually too late, and unidentified anonymous others from government who jump onto emotional bandwagons fuelled by often inaccurate and hysterical reporting in the media. Action is called for from hastily gathered teams of advisors and experts who are often divorced from what is happening on the ground. Resources limit what government agencies can achieve.
Protected zone status has some impact; plant passports are effective but can be doctored; and the sheer volume of imported trees coming into the UK is actually unknown. Individual nurseries in most cases carry on with business as usual. There has been little focus on the end user, the person who actually specifies and or buys the trees, such as garden designers and landscape architects. But it is here that the choice is made – whether to use directly imported tree stock transplanted directly into the UK landscape – and perhaps where the greatest impact on biosecurity can be made. Surely it is up to every user of trees to look in the mirror and consider their own working practices with regard to biosecurity and then act in a responsible fashion?
So what can the individual purchasing plant material do? A first stage would be to avoid going directly to a nursery outside of the UK for supply of trees that are going to be planted directly into the UK landscape.
A second stage would be to ask the UK nursery supplying trees the following questions:
Have you got a written biosecurity policy? How long have the trees been on your nursery? What pest and disease control programmes have been applied while the trees have been on the nursery? Is there a complete documented audit trail which confirms the above and confirms that all legislative plant health requirements have been met? Does this audit trail apply to whole batches of trees which may have already been shipped out for planting into the UK landscape where the subsequent emergence of a particular pest and/or disease is identified? Can the whole batch be recalled or destroyed? Can I come and see the trees I am ordering at your nursery? Do you, as a nursery, make any other provision to ensure that the trees supplied are in optimum physiological health prior to despatch?
If the answer to any of these questions is no, then an alternative supplier should be sought. To provide the range of species, cultivars, and size of trees required by the UK market trees will always have to be imported but safeguards can be built into the system.
Oak Processionary Moth is now spreading outwards from London. It is a public health hazard. It was brought into the UK on a single oak tree imported and planted directly into the landscape. Someone, somewhere is directly responsible for the importing of this oak and someone somewhere will be directly responsible for the next outbreak when it occurs. Please don’t let it be you.