The Defra action plan has an air of sanity conspicuous by its absence from every other domain of government policy. The ban on imported ash trees remains in place; no ash is to be moved around; diseased trees in nurseries and young plantations have to be destroyed but established trees with signs of dieback need not come down: how will we identify resistant strains if every tree is felled at the first sign of infection? (C. fraxinea, Defra added, does not move directly from a diseased tree to a healthy one, but ‘only via the leaf litter’.) For the moment there is relative calm, even if the prognosis for Britain’s population of common ash (fraxinus excelsior)

Plants have always been moved about – it’s a point Rackham makes – but a voyage on a sailing ship was long enough for a pathogen to die, or kill the specimen, before arrival. On a steamship the odds of survival improved. C. fraxinea is one of many globetrotter diseases attacking oak, chestnut, alder, Corsican pine, new generations of elm and several other species, in a world of 24-hour deliveries.

The fungus has been detected near the Channel and it has taken firm hold in the woodlands of the Haute-Saône in north-eastern France. The French, who are normally interventionist (they spray their oak woodlands from helicopters), have struck a fatalistic note on C. fraxinea, which arrived about five years ago. They made the same case against felling that Defra made in November, but they believe the fungus extends its territory at a rapid rate, moving at 150 km a year, against the Woodland Trust’s estimate of 20-30 km.

Wait-and-see has prevailed over a policy of widespread felling, but another line of argument will open up in the spring and summer as existing damage becomes visible and the disease makes seasonal headway. The idea that C. fraxinea can be zapped with a clever chemical is not fashionable: conservationists don’t like it, scientists doubt it can be done and governments are uncertain what products it’s appropriate to license.

http://www.lrb.co.uk/v34/n23/jeremy-harding/diary

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