Trees in Britain are under attack from diseases we hadn’t seen before. Emerging diseases. The dieback fungus Chalara fraxinea on ash (Fraxinus excelsior) isn’t the only emerging disease threat to trees in Britain.
There’s also Phytophthora ramorum, another fungus or ‘fungus-like pathogen’. This one attacks the Japanese larch (Larix kaempferi), the European larch (Larix decidua) and other trees and shrubs. P. ramorum was recorded on L. kaempferi in Northern Ireland in 2010 and in that same year, on L. decidua near some L. kaempferi in Cornwall. On various trees and shrubs this pathogen has been spreading through Britain since 2002. Here’s what the Forestry Commission says about its P. ramorum control programme in England. Last month larch trees in Scotland started to be felled in an attempt to control the disease. Will this turn out to be too little, too late?
Another emerging threat is Pseudomonas syringae pv. aesculi, a bacterium affecting the horse chestnut (Aesculus hippocastanum). This bacterium causes bleeding canker. The disease has become more common within the last four years but the Forestry Commission isn’t calling this a crisis.
Clive Potter at Imperial College says that we’re importing too many trees. Dr Potter says that controls should be tightened to stop tree diseases reaching Britain from all over the world.
[Edit] Steve Woodward and Andrea Vannini tell us about invasive alien pests and pathogens threatening European forests.