Friday, 2 November 2012
Ash die-back – cures far worse than the disease.
Late in the day – probably too late in the day – we have woken up to ash die-back (Chalara fraxinea). Indeed, at last government seems to be taking tree diseases in general more seriously. However, if we fall into panic mode then we could come up with a whole host of “cures” that are far worse than the disease.
The first reaction was to cut and burn infected trees. This could only possibly work if the disease had not progressed far. If caught in time, with just a few trees affected, then there could have been a policy of cutting infected trees and also removing trees in the vicinity in order to prevent spread.
Increasingly, however, the evidence seems to indicate that the disease is now established in the wider countryside, and that spores may be spreading on the wind. The genie may now be out of the bottle. Far from helping, a slash and burn approach now may be counter-productive. Some of our ash trees may have resistance to the disease. If we destroy all ash trees in sight then any new race of resistant ash trees will never emerge. Acres of dead ash trees, killed by the disease, will be bad enough, but a scorched-earth landscape with no chance of ash tree recovery will be far worse.
We are now also seeing the emergence of some most bizarre ideas for a “cure”. Recent news reports suggests that “scientists” have come up with a “cure” and it is only “red tape” that is holding things up. This cure is the aerial spraying of a solution of copper sulphate and nutrients, presented as a modern answer that just requires fast-tracking through trials.
On the contrary, the use of copper sulphate as an anti fungal agent is centuries old – throwing it out of an aeroplane does not make it a new cure and goodness knows what any “trial” might show that we don’t already know! This is a highly damaging broad-spectrum fungus-killer. It will kill a wide range of fungi, could well persist in the soil and might fundamentally damage woodland ecosystems. Our under-rated fungi are the engines of woodland ecology. They recycle all the nutrients, form soil and enable plants to grow. Without them our environment would simply not work. Tipping chemicals into woods in the hope of curing ash die-back is about as likely to be helpful as is randomly jamming a screwdriver into the back of a computer. Indeed it is quite possible that we are seeing an increase in diseases because our fungal flora is already unhealthy. The broad-spectrum killing of more fungi is not the answer.
This underlines the point that government needs to take proper advice on this subject from people who know something about woodland ecology. They should not simply fall for any wacky knee-jerk reaction.
In the end I suspect that the only sensible course now is to let nature take its course and try to encourage a new generation of resistant ash trees.