March 22, 2012
The fungus that wiped out 3.5 billion chestnut trees in the USA has been found for the first time in Britain. Chestnut blight, caused by the fungus Cryphonectria parasitica (C. parasitica), has been confirmed by Forest Research scientists on trees in two small orchards of European sweet chestnut (Castanea sativa). The trees were imported by an English tree nursery from the same grower in France. The sites in Warwickshire and East Sussex are the first findings in Britain. Until now, the English Channel had prevented its spread from mainland Europe.
The fungus infection is usually fatal to European sweet chestnut and its North American relative, Castanea dentata, although it appears to be less virulent in Europe than it is in America. It is believed to have first originated in Eastern Asia before being introduced to North America in the late 19th Century, where it has since devastated billions of trees in the East of the country (see The American Chestnut Foundation). It was first identified in Europe in 1938, in Italy, and has since spread to most parts of southern Europe where sweet chestnut is grown, and to parts of northern Europe.
Identifying chestnut blight
The most obvious symptoms of chestnut blight are wilting and die-back of tree shoots. Young trees with this infection normally die back to the root collar, and might re-sprout before becoming re-infected. Other symptoms, such as stem cankers and the presence of fruiting bodies can also occur.
The trees where the fungus were discovered had been imported into the UK for nut production. As I have written before (e.g. Climate Change and Global Trade), the import/export of trees is potentially the most significant factor in the spread of new tree pests and diseases. Case proven I think. Let’s hope that FERA (Food & Environment Research Agency of the UK Government) is given adequate resources to tackle this very serious fungus. Afterall, sweet chestnut is a beautiful tree species in our forests and when coppiced, as it is in commonly in Kent (see Sweet Chestnut Coppice), it is one of the few forest systems that pays well and regularly.