September 21, 2022
In recent years there are and have been many diseases and pests that threaten our nation's trees and woodlands. Much of the risk is created through climate change and global trade, with increasing freedom to travel and limited resources for checks at international borders.
Dutch elm beetle back in the '70s, was and still is responsible for the destruction of tens of millions of trees following its accidental introduction. More recently we've seen red band needle blight (Dothistroma septosporum) massively impact Corsican pine yields, and Ramorum disease (Phytophthora ramorum), which killed huge swathes of larch trees, particularly in the west of the country. Most recently and perhaps the most notable of them all is ash dieback (chalara or Hymenoscyphus fraxineus), which is widespread throughout the UK. This fungal pathogen is expected to wipe out around 80% of our common ash - the most prolific deciduous native. However, there is now another threat to the UK's woodlands.
Spruce, which accounts for around 60% of our conifer woodland area and is by far the UK's most commercial species, is at risk from Ips typographus, more commonly referred to as the eight-toothed spruce bark beetle. If left uncontrolled this beetle has the potential to be more devastating than those mentioned above.
Ips typographus usually attack stressed or weakened trees, although their numbers can increase under certain conditions leading to a 'mass attack' which overwhelms the natural defence of healthy individuals, or a group of trees, ultimately leading to tree mortality.
A large-scale Ips typographus outbreak has the potential for massive damage to the UK’s woodland and timber industry.
Ips is already present throughout continental Europe, and there has only ever been one outbreak confirmed in the UK, resulting in the Plant Health (Ips typographus) (England) Order 2019. This remains in place today and restricts the movement of all spruce from parts of Kent and Sussex.
However, following routine Forestry Commission plant health surveillance activities earlier this year, there has unfortunately been a confirmed presence of additional breeding populations, as confirmed by Nicola Spence, UK Chief Plant Hygiene Officer “Two outbreaks of the eight-toothed spruce bark beetle have been identified in the Kent forest area. This beetle does not pose a threat to human health, but it can have serious implications for spruce species and forestry.
As part of an established biosecurity protocol used for tree pests and diseases, rapid and powerful measures have been taken to limit the spread of outbreaks, and legislation restricting the movement of spruce in the region has been enacted.”
Several amendments have already been made to the order in an attempt to help minimise and suppress the spread of this pest, once in July, and more recently in October 2021.
Both amendments resulted in larger demarcated areas being established, now including the counties of Berkshire, Buckinghamshire, Hertfordshire, Surrey, City and County of the City of London, Greater London, West Sussex, East Sussex, Kent and Essex, as shown in figure 1 below.
Within this zone, the movement of all potentially infested or untreated material with bark present is strictly prohibited. All forestry works can only be carried out under a movement and processing license, issued by the Forestry Commission.
This new larger demarcated area will see an increase in surveillance and biosecurity management activity, meaning tougher movement restrictions and access to limited sawmills and timber processing facilities.
Despite this, it has become clear that Ips typographus outbreaks in spruce-dominated forests after significant disturbance cannot be prevented. We can, however, slow down the spread and minimise the risk of damage to living trees by applying tough woodland management techniques and eradication measures such as:
Removal and felling
The timely removal of wind-thrown timber is an important factor in the management of I. typographus, as this removes the ideal breeding substrate. Sanitation felling of infested standing trees is the most effective control method for large areas and needs to be undertaken during the winter months when adult beetles are not active. It offers the best chance of avoiding mass propagation, providing that the operation is undertaken with care and good planning. All normal forest operational planning also needs to be undertaken to ensure site hazards, ground conditions, diffuse pollution and site safety management is in place.
Initially all of the worst affected standing trees should be felled and chipped on-site, along with any windblown and newly dead trees as these provide prime habitat for beetle infestation. All material must then be transported under license to an authorised processor, where it can be dealt with in a controlled manner.
Mass trapping with pheromone-baited traps or trap trees can be an effective method for reducing beetle numbers and protecting healthy living trees, especially when placed on the edge of the woodland as this can act as a protective barrier.
Infested logs can be sprayed with insecticide to stop insect development and cause significant mortality. Healthy trees can be treated as a preventative measure, although this will only be effective if applied prior to adult beetle infestation. Individual tree treatments, however, are not practicable in a large-scale operation.
With several offices in the South East including Bedgebury in Kent, Coombes are well placed to help deal with this threat and are already working closely with Forestry England plant health advisors. Forest management and harvesting expertise, coupled with our relationships with timber hauliers and processors allows us to harvest, transport and market timber originating from your forest or woodland within the demarcated area.
Woodland managers, land owners and tree nurseries are urged to remain vigilant. If anyone suspects a sighting of a bark beetle they are advised to report it to the Forestry Commission through the Tree Alert Portal.