The threat of ash dieback
As National Trust places across the country are faced with one of the worst years on record for cases of ash dieback disease, Ickworth Ranger Matt Bevan takes a closer look at work underway at Ickworth to tackle the spread on the estate.
What is 'ash dieback'?
When we talk of ‘ash dieback’, what we are referring to is the decline of ash trees as a result of the fungus Hymenoscyphus fraxineus (you may also have heard this called Chalara ash dieback). This has been in Europe for around 30 years, but first recordings in England were in the South East in 2012, likely to be from imported ash saplings carrying the fungus. The fungus spores can also travel on the wind for miles and once established cut off a trees ability to absorb water and can then lead to further infections by other pathogens causing further decline and death.
How has Ickworth been affected?
An ash tree of 20-30 years old with the disease will decline over a few years before eventually dying in around five years. Larger trees seem to be more resilient although are still showing signs of dieback. At Ickworth, around a quarter of our woodland is ash (60ha) plus there are ash trees across the parkland. Our current situation is that around 75% of our ash is infected with the disease and in some stage of decline.
What do trees with ash dieback look like?
What you will mainly see are very few leaves on the branches which have either died back this year, or over years as the condition worsens branches die off altogether and will not produce any leaves at all. These become brittle and could then snap, an issue if the tree is over the path. Over time, more major sections of the tree may also weaken and larger sections could fall, and potentially the whole tree could come over in time.
What are we doing?
Given the scale of this issue now, National Trust places carried out surveys of ash trees across areas used by residents or visitors , which will enable a plan for the next few years to be drawn up.
For Ickworth, this has meant surveying all property boundaries, gardens, car parks, play area, Multi Use Trail and all other waymarked trails and took several weeks to complete. The aim was to identify ash trees with at least 50% canopy loss which is thought to be the stage that the tree will not recover and so will pose a safety risk in the near future and will need to be dealt with. Whilst some trees are only just at this stage, others are nearing the stage where they are completely dead.
You may have noticed pink spray dots on ash trees if you have been walking around Ickworth. We identified more than1,100 trees with at least 50% canopy reduction, half of which will need to be dealt with by contractors due to their proximity to buildings, power lines or such like and so will require specialist equipment to dismantle safely which will be a significant cost to the Trust.
The other half can be dealt with by experienced in house felling teams at Ickworth. The main areas where there are significant numbers of trees are the Trim Trail and sections of the Multi Use Trail in Lownde and Lady Katharine’s Wood. Main routes such as these will be kept open in the long term, however less well used routes with large numbers of infected tress may have to be closed off for a while.
How long will this take?
This will be our main priority of our winter work from October through to February, over the next two to three years. Our usual work of coppicing, ride widening, tree planting and Veteran Tree management will unfortunately have to wait as this takes priority. The timber in the main will be able to be used for firewood, milling and also for the biomass boiler rather than extracting softwood, and again this will take significant staff time to collect and process.
If this work was not done now, not only is there the safety risk, but also some of the smaller trees would degrade too far to use.
But it isn’t all bad news, there will be benefits too, including opening areas of woodland up, letting more light in and encouraging flowers, scrub and natural regeneration of other species, although the loss of ash trees will be a significant natural and cultural loss. Many other insects, invertebrates, lichens and mosses rely on ash as their habitat, and the timber is valued for a wide range of uses.
Some trees are not showing signs of dieback, and so these will be left and monitored in the hope they have resilience to the disease.