Background

Today, it is not an understatement to say that the survival of Britain’s natural environment is at a crossroads.

The nature and extent of the virulent non-native tree diseases now present in the UK promises a grim future for our countryside and urban trees. The number of diseases has grown alarmingly in the last ten years and local outbreaks have now become national epidemics.

In the 1970s, Dutch Elm Disease (DED) devastated the British countryside – and did similar damage across Europe. DED killed over twenty five million elm trees in the UK and now, forty years later, the elm trees haven’t come back, despite efforts to breed ‘disease-resistant strains’. Today, virtually all our deciduous tree species face similar threats from a barrage of non-native fungal and bacterial pathogens.

Ash under threat

The impact of Chalara fraxinea (Ash dieback) has been massive and widely reported. Over 80 million ashes are under threat in the UK from a pathogen which attacks through the leaves. Evidence from Poland and Denmark shows that tree mortality is high – as high as 98% over a period of 8-10 years. A few trees may be showing resistance, raising more false hopes of regeneration.

Danish forest experts advise that there is nothing than can save our ash trees. The Danish view is based on the fact that 95% of their ash trees have been infected and will die.  The real lesson here is that the Danes didn’t fight to save their trees.  Neither did the Poles or any of the European countries where ash has been devastated.   We can’t accept that laissez-faire attitude, but there was, perhaps, an underlying reason – that no effective treatment was available. The loss of these trees will have a major impact on UK woodlands in many parts of the country. In the Lake District, it will scar a uniquely beautiful landscape where over half a million individual ash trees dot the hills and valleys. Some of the UK’s finest and oldest ash specimens are to be found in Langdale, Borrowdale and Ullswater.

The potential loss of our ash trees is just the tip of a very big iceberg.

Horse Chestnut under threat

Forestry Commission studies in 2007 estimated that over 50% of Britain’s two million horse chestnuts were infected by Pseudomonas syringae (Bleeding canker). This figure is now believed to be close to 70% and rising. Bleeding Canker kills gradually and we believe it can be treated but, unless action is taken, a great many of the UK’s beautiful horse chestnuts will be lost within the next 10 years. Look around – many are being taken down already.

Oak and larch under threat

Oak and larch are in danger from Phytophthora ramorum, a fungal disease that slowly chokes and kills. The severity of this problem is underlined by the remedial efforts in Cornwall and South Wales where more than 4 million larch trees have already been taken down in an attempt to create a buffer zone to prevent spread. Alas, the nature of this highly mobile disease has already rendered the operation futile and the disease has quickly spread, as far north as Argyll.

There is more. Many oaks are suffering from Acute Oak Decline caused by a bacterial infection which is still being researched.

Beech, Juniper, Cypress and Alder under threat

The Phytophthora genotype is particularly worrying. Over 100 Phytophthora variants have been described and as many as 500 more are believed to exist. They attack a very wide range of plants – from mature trees to commercial crops, and do £billions of damage worldwide each year. Further variants, Phytophthora kernoviae (attacking European beech and many ornamental plants) and Phytophthora austrocedrae (juniper and cypress) are now becoming widespread in the UK. Phytophthora alni is attacking Alder and seriously damaging riparian systems all over the UK. Phytopthora cinnamomi, which attacks a wide range of trees and ornamental plants, was first identified in the UK in 2001 and is present in around 50 other countries.

London plane under threat

Splanchnonema platani has arrived from Germany and Holland. It targets the London plane – a tree which lines thousands of urban streets and causes dangerous instability as the tree fights the infection by shedding branches.

Sweet chestnut under threat

Cryphonectria parasitica is a disease of the sweet chestnut which has decimated America’s indigenous chestnut forests and, with two recent cases discovered in the UK, now threatens a thriving forestry industry in Kent and Sussex.

A worldwide problem

Around the world, Phytophthora ramorum is the reason why the famous oaks of Monterey are dying in their thousands and the USA is losing millions of trees each year to a juggernaut of imported pests and diseases. In France, Ceratocystis platani is rampant and the planes and poplars lining the historical Canal du Midi are being felled, causing damage which is difficult to comprehend.  In Spain, vital food crops such as citrus, olives and nuts are being threatened by evolving Phytophthora strains. Even isolated and supposedly bio-safe New Zealand is facing a disaster as the kauri trees die (Phytophthora taxon Agathis).

This is still not a comprehensive list and the environmental issues are significant. On the upside, we have now tested CuPC33 successfully, not only against Chalara fraxinea but also against Phytophthora cinnamomi, Massaria platani, Ophiostoma novo-ulmi, Cryphonectria parasitica, Armillaria mellea and Venturia inaequalis.