The story of the discovery of the fungus Chalara fraxinea in ash trees growing in the United Kingdom is unfolding with bewildering speed.
Chalara fraxinea kills most of the ash trees it infects and is responsible for the phenomenon that has become commonly known as ‘ash tree dieback’. There is no known treatment for ash tree dieback nor any known way of protecting trees against it; unlike us, who can be vaccinated to give us protection against quite a number of infections, there is no known way to vaccinate trees. And the sobering truth is that fully 75% … that’s three-quarters … of all the ash trees in the United Kingdom are facing the possibility … some would say, the probability … of being killed by this disease.
Since the problem has been known to exist on the European mainland for a number of years, one obvious question is to wonder why it was able to enter our islands. After all, there are strict controls in place to prevent unwanted animal infections from crossing the North Sea … the most significant being rabies … so why are such controls not in place for plant diseases? And the short answer is that there are controls on the import of plants; those of us who pass through customs and immigration on our way into this country know full well that, in general terms, it is unlawful to bring plants into this country without a licence. But, setting aside the fact that the disease, which is very difficult to detect in its early stages, has been found in legally-imported ash tree seedlings, there is also the distinct possibility that it was blown across the North Sea by an easterly wind or imported inadvertently by travellers.
We travel very much more extensively than any previous generation; we enjoy exotic imported fruits and vegetables on our dining tables and exotic plants in our parks and gardens; and, as well as importing those things that we want, we inevitably bring with them things we categorically do not want. And we do want ash trees. Although the tree is a native species to the United Kingdom, economic pressures have led to a big decline in the number of British nurseries producing ash trees for commercial growers, just as the ‘British’ clothing industry sources a great many tailored and woollen garments from countries where these can be made more cheaply than we can make them. So nowadays we import saplings of a hardwood that is tough, very strong and remarkably elastic; we use it to make tool handles, baseball bats, hockey sticks and similar products; we use it extensively in interior joiner work in homes and offices; and we use it as a veneer for office furniture, for it is machine-friendly, accepts nails and screws willingly and can readily be glued to other surfaces. And, when the joinery, furniture and sports goods trades have finished exploiting the timber and have used all the bits they want, the left-overs make excellent wood for the food industry to use in smoking fish or meat; and, at the very end, the scraps are great in garden barbecues.
As well as being grown extensively by the forestry industry, ash trees are found growing wild throughout these islands; they are often used in low-maintenance decorative plantings by local authorities; and the more attractive varieties make eye-catching specimen plants. But if ash tree dieback does in these islands what it has done in Demark, where it is believed that 90% of all the ash trees have been killed, our familiar landscape will be changed … and changed forever in human terms. Mother Nature usually manages to change plants to make them resistant to the diseases they meet: but, though it is likely that naturally-occurring genetic mutations will result in the appearance of an ash-dieback-resistant species, Mother Nature tends to work slowly, so this may take hundreds of years; and, since I don’t expect to live long enough to see such trees, I must hope that scientists will intervene very soon.
Sandy Simpson, Polmont Horticultural Society