Ash dieback: felling trees not always necessary, research suggests

Felling trees affected by ash dieback may not be the only option available to farmers, experts believe. 

Researchers at the University of Copenhagen have warned against automatically felling affected trees, believing instead that pruning dead branches is sufficient. Entire trees should only be cut down if they are dead, dangerous or no longer contribute any value to the landscape.  

“This research from Denmark, where the disease has been prevalent for a decade, suggests prompt removal of affected trees might not be the best or only way of managing the problem,” said Marc Liebrecht, forestry specialist at Carter Jonas.  

“On that basis, it’s advisable to identify risks and fell only high-risk trees, giving others a chance to either die naturally or recover and aid resistance development. 

“If they pose a risk to roads and people, then they should be dealt with, but if isolated with fields and not dangerous or troublesome, then leaving them alone to maintain biodiversity is preferable.” 

What is ash dieback? 

Ash dieback was first spotted in the UK in 2012, although it’s now believed to have been present for longer. The fungal pathogen causes severe leaf loss and crown dieback, either killing the tree or making it more susceptible to other fungi.  

Although this research provides a possible alternative to felling, farmers and landowners shouldn’t become complacent. Having a plan is still essential, particularly in high-risk areas. 

“If there is any sign of the disease, a tree survey should be carried out and professional advice sought,” Marc explained. “We recommend, even if there are no visible signs, that anyone who owns or manages ash should have surveyed any trees which are within a tree’s height of a road or footpath. If a tree survey has been carried out in recent years, the surveyor will have identified any ash dieback and suggested remedial works or monitoring. 

“However, many will have been surveyed before the infection spread and thus structural degradation rate is not fully known, so it’s advisable to update the survey.” 

Is felling necessary for trees affected by ash dieback? 

Where ash on roadsides or alongside footpaths show more than 25% canopy dieback, the common position is removal as quickly as possible. Even where ash is in non-public areas, it may still pose a risk – for example, to beaters during the shoot season.” 

In lower-risk areas, ash can be left so that trees which may be tolerant can be identified. It’s thought a small percentage of trees are tolerant, and these may allow future regeneration of ash.   

Ash dieback restocking and grant funding 

Grants are available for replanting and regeneration of larger areas of ash that must be removed. “Restocking payments of up to £2,750/ha are available via the Woodland Tree Health Restoration Grant in certain circumstances,” Mr Liebrecht said. 

“It’s recommended any re-planting is done with a diverse species mix to ensure future resilience to pests and diseases.”