‘Operation Scorched Earth’ to stop Ips typographus reaching Scotland

FOLLOWING the discovery of breeding populations of Ips typographus (larger, eight-toothed European spruce bark beetle) on at least 13 sites in south-east England (Kent and East Sussex), UK plant health authorities are undertaking a pre-emptive programme of felling for Norway spruce, the primary host of this beetle within its European distribution.

This is not the first time a ‘scorched earth’ type policy has been adopted to deal with a notifiable insect tree pest in Kent. Almost exactly 10 years ago, during the spring and summer of 2012, an even more ruthless programme was employed at Paddock Wood, eight miles from Maidstone, Kent, following introduction of Asian longhorn beetle (Anoplophora glabripennis) to the UK on wood-packaging material originating in China. 

Salient differences between the two relate to the areas affected and the spectrum of tree and shrub species succumbing to the chainsaw blade. While there are already 13 notified outbreaks of I. typographus covering a sizeable area of Kent and East Sussex, the single outbreak of A. glabripennis in 2012 was confined to a very small area of Kent. 

A freshly-initiated gallery with a breeding, female Ips typographus starting to lay eggs under the spruce bark. (Image: Stock)

However, the broadleaf tree-host range of Asian longhorn beetle is truly massive, while the host range of I. typographus is essentially confined to the genus Picea (spruce). Back in 2012, conifers, Eucalyptus and English oak were essentially the only trees left standing in the area where A. glabripennis was found. And the authorities did not mess about. Mass felling, clearance and incineration of affected and susceptible tree and shrub host material was conducted right through the breeding season for wild birds and irrespective of any tree preservation orders. What’s more, police were used to enforce the law against landowners and householders resisting Forestry Commission contractors who were tasked with the removal and destruction of any shrubs and trees (or indeed wooden fences) which could possibly harbour the pest.

READ MORE: Forestry Commission acts on European spruce bark beetle tree pest findings in Kent

And ‘scorched earth’ is no understatement. Air burners from Kingwell Holdings were used to incinerate material from all infested trees and all healthy, potential tree hosts within a 100 m radius around an infested tree. The operation started in late April 2012 and by mid-June 65 infested trees and 1,300 healthy, potentially susceptible trees had been destroyed over an 8-hectare area.

IPS TYPOGRAPHUS – UK INFESTATION ILLUMINATED

The current Ips typographus situation has been ongoing since December 2018, when the first established UK outbreaks were confirmed in the Ashford area of Kent. One was identified in woodland on FC land, with the other belonging to an NGO (non-governmental organisation) with a high national profile. Infested and susceptible trees – mostly Norway spruce but some Sitka – were felled to ground level and all affected material incinerated on site. 

Two more outbreaks were subsequently discovered on June 25 and July 1 2021, during routine surveillance operations. After an extensive follow-up surveillance, a total of 13 outbreaks were recorded in Kent and East Sussex by the FC. The original demarcated area (most of Kent and a sliver of East Sussex), related to the December 2018 outbreaks and covering restricted movement of specified material of the genus Picea (spruce), has been revised several times. The current demarcated area, which became effective on 22 December 2021, is covered by the Plant Health (Ips typographus) (Demarcated Area No. 4) Notice, which now covers a very large part of south-east England as follows: 

• the entire land area of Kent and East Sussex
• the majority of West Sussex and the eastern side of Surrey
• London, including those parts of Berkshire, Buckinghamshire, and Hertfordshire inside the M25 motorway
• a large portion of Essex from the county boundary with Greater London; inland from the coast as far as Chelmsford and as far north as Clacton and Colchester 

All notices are issued under the Official Controls (Plant Health and Genetically Modified Organisms) (England) Regulations 2019.

Affected and potentially susceptible Norway spruce at the first found outbreak sites near Ashford in Kent in December 2018 was incinerated on site using air-burners. Mulching appears to be the preferred game for the more recent outbreak sites in Kent and East Sussex (picture courtesy of Kingwell Holdings). (Image: Kingwell Holdings)

A number of press releases have been issued by the FC, but as is generally the case for reports of new pests and diseases, they are very short on detail. At no time has the general public been informed of the exact locations of these outbreaks, the species, size and age of the trees affected, or the nature of the ecosystem (e.g. mixed woodland, plantation monoculture or scattered trees in parkland). 

Also notable by its absence is an assessment of whether infestations are on trees which were already diseased and/or stressed, or trees which were healthy and vigorous when invaded by Ips. Ips typographus is generally considered to be a ‘secondary invader’, exploiting trees which are already unhealthy and/or under physiological stress. However, it is widely reported to also attack healthy trees, particularly when pest populations have been allowed to build up into high numbers over a long period of time. Clearly related to this is assessment of how long these infestations have been going. 

However, in a significant departure from normal procedure and practice with regard to publicity, Nicola Spence, UK chief plant health officer with the DEFRA, was interviewed in December 2021 by the BBC Radio 4 programme Farming Today. 

From the broadcast, we learned the exact location of two of these outbreaks – Elhampark Woods (CT4 6AJ) and Beveridge Bottom Woods (CT4 6YE), both in Kent. These woodlands are close to each other and located approximately halfway between Canterbury and the coastal towns of Folkestone and Hythe. 

Ips typographus breeding gallery showing vertical tunnels created by two females with young larvae starting to feed.

The programme makers, who were apparently at one of the sites, said all Norway spruce within 300 metres of an infested tree were being destroyed and implied on several occasions that pine trees were also involved in the infestation and felling. 

They also interviewed local landowners who farm the land around the two sites and who expressed dismay about the 300-metre rule and how it would impact them – in particular how it would disrupt wildlife, with owls specifically mentioned. Without wanting to sound callous, they should perhaps be thankful this work happened outside of the bird nesting season, unlike aforementioned operations in 2012.

Claims that all Norway spruce, irrespective of size, are being destroyed don’t appear to match up with restrictions operating within the demarcated area and where Norway spruce trees under three metres appear to be exempt. 

However, perhaps the most significant comment from Nicola Spence was that all this is being done to stop any spread of Ips typographus into northern areas of the country, especially Scotland, where the bedrock of British forestry exists as huge areas of spruce trees. Sitka and Norway spruce jointly occupy 726,000 hectares, representing 55.5 per cent of all commercial softwood plantations in Great Britain. 

Nicola Spence expressed full confidence that these outbreaks in Kent and East Sussex can be eradicated. She told Farming World: “Larger hectarages of spruce, particularly in places like Scotland, that’s what we’re trying to protect. But we do think we can manage these sorts of single sites and eradicate the beetle from each of those.” Affected areas will be replanted with deciduous trees. 

Perhaps most enlightening of all was an apparent firm belief that these new outbreaks were initiated by adult beetles flying into southern England from the European continent during warm weather in June 2021.

INFESTATION ANALYSIS

Forestry Journal has since learned the exact location of several more of the 13 outbreaks. They are: Heane Woods (CT21 4HG), Darwell Wood (TN32 5JB), Beckley Woods (TN31 6RZ) and Haberdashers Wood (TN26 2EJ). Heane Woods and Haberdashers Wood are, respectively, six miles and 10 miles south-east of Ashford in Kent. Darwell Wood and Beckley Woods, though carrying Tonbridge (Kent) postcodes, are in the East Sussex Weald.

DEFRA and the FC have gone to great lengths to reassure the public over how new insect pests and diseases arriving and establishing in the UK ‘will not harm you and your pets’, ‘ruin your runner beans’ or ‘shred your shallots’. However, with Ips typographus carrying the full common name of ‘larger eight-toothed European spruce bark beetle’ I would certainly want to know the pest status before I took my mutt for a walk in the woods.

South of the River Thames, Norway spruce becomes increasingly frequent as you move into the Surrey Hills. Norway spruce being felled and extracted on Forestry Commission land in the Surrey Hills some 10 years ago. (Image: Stock)

Additional information given to Forestry Journal on the severity of the first two outbreaks near Ashford in December 2018 indicated a pest infestation in place for between two and three years before discovery. Erstwhile healthy and vigorous Norway spruce was attacked, which shows the severity of what had been building up over an extended period of time. Norway spruce, which is the primary host of this pest within its European distribution, accounted for the vast majority of trees affected, although on one site at least some Sitka also came under attack. 

A Forestry Journal reader who happened to be on one of the new 2021 outbreak sites in the Canterbury area of Kent was told by FC officers on site that the extent and severity of that infestation indicated it had been ongoing for up to eight years.

The million-dollar question, in relation to the future spread of existing outbreaks, with the likelihood that more are yet to be found and more yet to arrive and establish, is exactly how the beetle pest is getting into the UK and into what areas of the country. DEFRA and the FC appear adamant the 2021 outbreaks were initiated by adult beetles flying into the country from continental Europe in 2021. However, in light of the suggestion that outbreaks may have been in place for years, rather than months or weeks, any such theory should be investigated to see if it stands up to scrutiny. 

READ MORE: Mass felling operation underway in fight back against 'devastating' spruce bark beetle

These new outbreaks are established at points well into Kent and East Sussex (up to 80 km inland). Add on the channel crossing and the likelihood that beetles originated on trees away from the coast in France (or another country) means a flight distance of between 100 and 200 km, and perhaps even more, would have been required.
European research conducted over many years shows adult Ips typographus beetles can fly up to 4 km in search of suitable host material. They may also disperse over longer distances. Distances mentioned are in the order of 8 km plus, which is well short of the 100 km, let alone 200 km, indicated. 

DEFRA and the FC clearly state the first two new outbreaks identified on 25 June and 1 July were initiated by adult beetles flying in from continental Europe during warm weather in June 2021. And that breeding populations were also present at the Forestry England woodlands of Darwell and Beckley Woods in East Sussex (Weald) and Elhampark and Beveridge Bottom Woods in Kent when the outbreaks were discovered.

After a distinctly cool and wet May in 2021, when the temperature did not reach 20°C on a single day at Maidstone, June was indeed a much warmer month. Temperature records for Canterbury (Kent) show 23°C to 28°C on every day between 7 and 14 June. 

Spruce bark beetles, and Ips typographus in particular, ‘take no prisoners’ for trees in the genus Picea. (Image: FJ)

However, the time required for the development of a full generation of Ips typographus is between two and two and a half months. Male and female beetles need to locate each other and mate and eggs need to be oviposited by the female, develop and hatch into larvae. That doesn’t leave much time for the feeding larvae to appear and this was presumably the stage seen when the outbreaks were discovered. Furthermore, Ips typographus has been wreaking havoc for centuries in Europe, so you have to ask why this spruce bark beetle pest waited until 2021 to make a flying visit to England. 
Long-distance movement of Ips typographus is via spruce timber with bark. Indeed, the FC’s own contingency plan for Ips typographus, produced in 2015 prior to Ips typographus establishing in the UK, says the very same thing. 

It states: “Ips typographus is absent from the islands of Great Britain and Ireland, although it has occasionally been intercepted at British ports. In 1995, for example, 149 beetles were captured in pheromone traps deployed in 20 port areas. In 1997, approximately 30 adult Ips typographus were captured over 10 days at the Shotton Paper Mill in Clwyd. This mill processed spruce from British forests, so the beetles could have been of British origin. However, it is possible that they came from low-grade spruce used as wood packaging for machinery transported to the surrounding industrial area.

Follow-up surveys in forests around the mill, and from forests throughout Britain that supplied the mill in the four weeks before the trap captures, failed to detect the beetle.

However, along with further finds at ports, it confirmed that the beetle frequently enters this country in host material with bark. The impact on the UK’s spruce forests could be devastating if this pest were to become established in this country.” 

You have to ask whether it could all be down to botched biosecurity (inspection and quarantine), especially since Ips typographus is just one of a number of insect pests and diseases endemic in Europe for many decades if not centuries, but only arriving and establishing in the UK in recent years, such as oak processionary moth (discovered 2006), sweet chestnut blight (2011) and oriental chestnut gall wasp (2015). 

Recent analysis by the Timber Trades Federation, published by Forestry Journal, shows softwood is being imported in larger amounts and from a more diverse range of countries. Latvia, Finland and Germany accounted for 61 per cent (1.1 million m³) of the total softwood (1.8 million m³) imported in Q3 2021. This was 33 per cent up on Q3 2020. According to the TTF, around 50 species of softwood are in commercial use, with the most common being European redwood (Pinus sylvestris – Scots pine) and European spruce whitewood (Picea abies – Norway spruce). Most softwood imported into the UK comes from Sweden, Finland, Latvia, Germany and Russia. Ips typographus is endemic and a serious economic pest, with Norway spruce as the primary host, in each and every one of these countries.

And what exactly is the fate of all this timber arriving in the UK from Europe? A regular reader of Forestry Journal recalls being on a site in Austria where Norway spruce, infested and damaged by Ips typographus, was undergoing felling and clearance. Out of curiosity he asked the site manager to which local biomass burning plant the material was going. To his surprise the site manager said: “Much further than that, because these loads are destined for biomass burning in your own country, the United Kingdom.”

If these new UK outbreaks did come in on spruce material with bark, then beetles will have most likely entered through a port in south-east England. This begs the question as to whether Norway spruce timber imports are entering through other ports around the country and closer to areas in northern England and Scotland, where most spruce plantations are concentrated. Forestry Journal has learned of increased surveillance carried out across the country featuring pheromone traps sited along transects emanating from the south-east corner of England, where outbreaks have been found.

IS IT ENOUGH?

There appears to be a conundrum in relation to Norway spruce less than 3 m in height, whereby such trees are apparently being destroyed on outbreak sites, but are apparently not subject to restrictions within demarcated areas. 

Affected trees and susceptible tree host material were incinerated on site at the first two outbreaks near Ashford in December 2018, but not this time round, when on-site mulching appears to be one of the preferred methods of dealing with debris.

Precautionary felling of Norway spruce up to 300 m from infested trees might appear drastic, but research carried out in Germany shows that on emergence in springtime, the adult beetles can disperse up to 750 m in a single day.

ADDENDUM

The Plant Health (Ips typographus) (Demarcated Area No. 4) Notice which became effective on 22 December 2021 introduced the following conditions:
(i) Restrictions on the felling of susceptible material without prior notification. Landowners must provide notice of their intention to fell relevant material at least 14 days in advance of any felling in the demarcated areas. Felling may only commence once written authorisation is provided by the Forestry Commission.
(ii) Restrictions on the killing of trees (either by ring-barking, chemical injection or application, mechanical means, biological control or arboricultural intervention) of the genus Picea A. Dietre over three metres in height, without prior notification. All operations must be agreed in writing by the Forestry Commission.
(iii) Prohibition on susceptible material being left in situ, unless authorised in writing by a plant health inspector.
(iv) Prohibition on the movement of spruce (Picea) material with bark (for example, wood with bark, isolated bark, live trees over 3 metres) that has originated within the demarcated area. Provision is made to enable plant health inspectors to authorise movements and processing of spruce material with bark from the demarcated area where this can be achieved without risking the spread of Ips typographus. Authorisations can be requested using the appropriate application forms as follows:
• Application to receive and process Spruce 
V1  
• Authorisation to process Spruce V1.
For all information, contact: ipstypographus.authorisation@forestrycommisson.gov.uk.