Maintain ash dieback vigilance, say experts, despite slower than expected growth in cases

Relatively limited spread of ash dieback disease leads experts to advise against downplaying the ongoing threat to trees.

Blackford Wood: hit by disease - image: National Trust
Blackford Wood: hit by disease - image: National Trust

One year on from ash dieback hitting the headlines and threatening to kill Britain's 80 million ash trees, experts say the danger of Chalara fraxinea should not be played down despite just 607 cases being reported in the UK.

At the end of the first full season since being found in the UK (HW, 7 June 2012) and with the growing season over, UK sites are just double the number found a year ago. Last year, the Government warned that the disease would be "no less serious" than in Denmark, where 60-90 per cent of ash were lost, and said young ash would be killed "quickly".

A Forestry Commission representative said: "Despite continuing surveillance by the plant-health authorities and increased awareness and vigilance by tree owners and the public, relatively little spread of Chalara dieback of ash has been detected in 2013, apart from short distances in local areas from existing sites. We believe the warm, dry summer this year was generally not favourable for the fungus's fruiting bodies and spore release.

"This reinforces evidence that advances in the disease 'front', especially in east and south-east England, are likely to be more significant than the rate of spread from outlying sites, where detected spread has generally been infrequent and slow."

The Forestry Commission confirmed the trace-forward programme from nursery consignments is complete.

Silviculture International owner Ted Wilson said: "I'm cautious about the statistics. I hope we don't downgrade efforts on the back of news reports that understate the threat. We need to gather more information."

National Trust countryside operations manager Mark Courtiour stressed that there is hope for ash after the trust planted 6,000 ash trees at Blackford Wood in Somerset in 2001 but only 10 per cent were infected when they had the disease confirmed there this spring.

"The assumption was it would come in quickly and kill trees in a year or two but that hasn't happened so this shows there remains a possibility we can slow it down," said Courtiour. "It might only be 10 per cent are infected because of the weather, or it might be some are genetically more resistant.

"The commission should be doing more to understand it. Our concern is there has been something of a washing of the hands by the Food & Environment Research Agency (FERA). There's a resignation that there's nothing we can do. We're trying to say ash is an important part of tree cover so we ought to explore options."

Dr Glynn Percival said FERA is "spread thin" and has to deal with massaria and sweet chestnut blight. He added that lab trials with fungicides are effective but FERA stopped him from running proper trials because it is dealing with the research. However, mulching with plant-defence activators is proving "very promising".

KEY STAT

UK distribution: 237 woodlands, 346 recently planted sites and 24 nurseries - plus another 101 sites affected in Ireland - 607 sites affected.


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