Biosecurity

Authors: Chris Goulding
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2014, Issue N.Z.J.For. 59(2) 2014, pp 2, Aug 2014
Publisher: New Zealand Institute of Forestry

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Abstract: More years ago than I care to mention, before starting university I carried out my practical forest work on an English estate. As part of the work, we were cleaning a regenerating mixed hardwood stand on a valley side – cutting away competing woody vegetation to release the young trees. As this was limestone country the predominant species was English Ash, Fraxinus excelsior. Even by now, the trees will still not have reached middle age, valuations based on discounted present net worth meaning little to the estate’s objectives of management. The woodland now ought to be as beautiful as Ash hardwood forest can be. In 2012, Ash dieback disease entered England. Caused by the fungus Hymenoscyphus pseudoalbidus, previously known as Chalara fraxinea, leaf loss and crown dieback are quickly followed by death. The pathogen came from the continent where it first appeared 20 years ago and is now entrenched, most probably arriving from Asia. The fungus spreads rapidly and it is expected that very soon between 90 and 98 per cent of the Ash trees in Britain will die, uneven-aged mixed-species forests notwithstanding. There are currently no effective measures to mitigate or prevent the disease. Felling infected stands is of little use as the fungus lives in the forest litter. The ban on importing Ash saplings and nursery stock from Europe, imposed in October 2012, was too late.

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