- Explanation of the problem
- Letter to write to your garden centre
- Useful weblinks about the tree species and diseases- become familiar with them
- OPAL Tree Health Survey – for schools, church groups and individuals to take part -and contribute your results to national survey.
- New Juniper disease spreading since 2011 – and latest records of infections – Juniper (yes, from which one can make gin) is already rare in the wild in the UK.
1. The Problem
Ash dieback threatening the UK’s millions of ash trees…
Sudden oak death infecting larch trees…
When seventeenth and eighteenth century plant hunters like Joseph Banks returned from long sea voyages to introduce new species to England, they little knew the consequences of the trend they would inspire. During the years which have followed, the international plant trade has allowed many and diverse pests and diseases to cross the world – from the gall wasp, which first came to Britain in the 1830s, to Phytophthora ramorum (sudden oak death), which is striking Scotland and Wales.
In recent years the scale and rate of the problem has exploded as more and more new diseases develop; and climate change may intensify some losses to these diseases, as well as to insect pests. Biosecurity needs to be improved – only 2% of cargo is inspected – but this is a complex issue. There are other solutions, which – fortunately – are less dependent on institutional reform.
Garden centres play a central part in introducing hosts and vectors : sudden oak death and ash dieback were first detected in Britain in garden centres.
Gardeners – one way you could help would be to buy smaller trees to grow on yourselves, instead of the now common tendency to plant large trees – which are not only more likely to harbour pests and diseases, but which are also far more difficult to inspect.
Limiting plant imports altogether remains vital.
2. Could you send the following letter to the manager of your local garden centre or plant nursery, asking them to sell only UK-sourced and UK-grown plants ?
And ask questions ! When you buy plants, ask where they are grown.
Dear ………….. (name of garden centre or plant nursery),
Ash dieback (Chalara fraxinea) and Sudden oak death (Phytophthora ramorum) are still in the news and striking more and more locations : and they are only two of many tree diseases which are infecting diverse species in the UK. The recent surge in the rate of new pests and diseases identified every year poses many problems, and I feel that every garden centre and plant nursery has a clear opportunity – and need – to address this question.
One of the most important players in this surge is known to be the international plant trade : importing ash plants to garden centres was found to have introduced invasive ash dieback to the UK, while Phytophthora ramorum was introduced on a viburnum also imported by a garden centre. The Phytophthora family of moulds has been diversifying
at faster rates for the last twenty years – and in the warm, moist conditions of a plant nursery, native and introduced diseases quickly hybridise.
Alongside diseases, pests also depend on international trade to colonise new areas. The citrus long horn beetle was introduced on imported ornamental acers – just one of many such pests.
Tree pests and diseases threaten not only individual species but also the entire ecosystem of which these species form a part. Moreover, they may cause thousands of trees (many in the UK’s few remaining ancient woodlands) to be felled to contain outbreaks, as we are seeing with larch trees in Scotland and Wales.
In order to limit the introduction of such invasive diseases and pests, I would therefore ask you to consider selling only UK-sourced and UK-grown plants wherever possible.
3. Notes on Tree Diseases on Ash and Oak:
Scottish government paper on Ash Dieback:
Phytophthora ramorum belongs to the same genus as Phytophthora infestans, the fungus-like organism which causes potato blight
4. Take part in the OPAL Tree Health Survey:
There are OPAL surveys on a variety of Topics – Lichens and air pollution (from Nitrogen compounds now, not Sulphur dioxide pollution); Ponds; and now on Tree Health. They are good for individuals or school or smalll church groups – and you contribute your results to the national surveys.
The latest is the Tree Health Survey (Your web editor went on a training morning last year for this) –
It is simple to do and you send in your results whether or not you find evidence of tree disease – and if you think the tree you are surveying might be diseased you are encouraged to send in a photo. You can download instructions on how to do the survey from the web, or send off for a pack.
5. – Phytophthora austrocedrae on Juniper – and happening as I put this post up.
Do you know how many native conifers we have in Britain?
Scots Pine, Yew and Juniper.
All other conifers have been introduced.
Juniper is rare. In Yorkshire it grows wild on the side of Ingleborough and on a hillside in Swaledale, and it grows in Teesdale. (and it grows in other places in UK – but your web editor lives in Yorkshire) It does not regenerate easily. Many studies have been made over the past 50 years or so to try and understand why it is declining. Now a new disease has struck: Phytophthora austrocedrae This has been affecting trees in Chile and Argentina for at least 50 years and was first confirmed in 2011 in Britain in wild Juniper bushes in Teesdale and and in single specimens of Lawson cypress and Nootka cypress trees at garden sites in Scotland. You can see its current distribution as of November 2013 here but I heard in November from a local naturalist that it has struck the site on Ingleborough near where I live.
Indeed this week I had an email from a Natural England Officer from our area
“I’ve some bad news in that Phytophera austrocedrae has been confirmed in juniper up Juniper Gill and on Moughton Common and which is usually fatal to the shrubs once infected. As of today a Plant Health Notice has been slapped on ourselves for part of the NNR and the Commoners part of which will be to discourage access and encourage biosecurity of cleaning boots etc. when accessing/leaving the area. You may wish to alert local naturalists to limit any leisure or recording use of the area, not to collect or remove plant material and clean boots and any other kit before gardening etc., especially around conifers/ shrubs that could potentially get infected.
Please write to your garden centre.
And let us know of any responses