Ips typographus: Are forestry officials right to be confident?

THE alien invasive spruce bark beetle Ips typographus continues to crop up in the UK, with the latest discovery in Scotland the scariest identification so far, given the bulk of commercial forestry in the country is based on Sitka spruce. An initial finding was of a single beetle picked up in an improved insect pheromone trap, deployed as part of Scottish Forestry’s new surveillance programme. However, to put that into context, SF said it was just a single Ips beetle found amongst 6,500 other insects covering 40 different species. But in December, the government agency announced a second beetle had been discovered in another nearby trap, bringing the confirmed sightings to two. 

• READ MORE: 'No evidence' spruce-killing Ips typographus is breeding in Scotland

The original beetle, found in woodland in Fife, is believed to have arrived on the back of goods being shipped into Scotland via the port of Grangemouth. Now, my knowledge of Scotland, in both geography and trading patterns, is notoriously sketchy, so I checked both the relevant geography and the nature of trade going through Grangemouth to learn: Grangemouth is on the Firth of Forth within the county of Stirling and Falkirk, historically in the county of Stirlingshire but now falling within the unitary authority of Falkirk – and just two miles south-west of the border with Fife.

So what about trade aspects? Grangemouth is one of the Forth Ports and Scotland’s largest individual port, handling nine million tonnes of cargo each year through liquid, specialist container and general cargo terminals. Imported goods include food, drink, machinery, steel products, paper and timber, the latter being the import of interest here. 

Forth Ports has a dedicated forest products terminal at Grangemouth and there will apparently soon be a massive biomass-burning plant operating at Grangemouth.

When planning permission was granted back in 2013, objections were raised by Green MSP Alison Johnstone, who said the plant would burn up to 1.5 million tonnes of imported wood every year. There has been no mention of where the wood is likely to come from and the sort of tree species, but conifers including spruce are likely to be involved and sourced from continental Europe where Ips has run riot for centuries if not millennia on Norway spruce. Clearly it remains the easiest and cheapest source of foreign wood earmarked for biomass burning in the UK.

There has been no mention of what port the wood for biomass burning was likely to come in through, but for proximity and economy Grangemouth would appear to be the obvious choice. 

I use the term ‘wood’ advisedly, because material for biomass burning is likely to be below grade, more likely to suffer from pest infestation and perhaps less likely to undergo as thorough inspection as high-grade timber for cutting and construction.

If the Ips typographus beetles did indeed come in through Grangemouth as SF implies, and specifically within imported bark-covered spruce timber or wood, then I would not choose the term ‘hitch-hiked’ to describe the pests’ ride into Scotland.

Scotland is lucky if these findings are indeed a one-off, which SF says they are – and a lot more fortunate than England, where established breeding populations of Ips have been found since 2018. The first was in Kent, with subsequent findings in East and West Sussex and then Surrey, with over 40 outbreaks reported by August 2023 and apparently all on Norway spruce.

Scottish Forestry believes its two findings – classed as a single interception – are a one-off. (Image: Stock)

The UK government said: “Outbreaks have resulted from natural dispersal (blow over) of Ips typographus from the continent. There is no evidence of onward dispersal from any outbreak site in England.” The type of evidence on which this assumption is based has not been specified.

It’s all very interesting, except decades of research across continental Europe strongly suggests the maximum flight distance capability does not match the distances these adult beetles would have to fly from France to reach southern England – especially if starting their journey a good way inland in France and then flying all the way to the Surrey Hills. Maps which display the distribution of Norway spruce in France show how you need to travel a good mileage eastwards from the coast before encountering high concentrations. 

For instance, the flying distance required to travel from Reims (140 km to the north-east of Paris) to Guildford in Surrey is 471 km. A broad range of studies carried out in Europe over at least half a century have come up with many different flying distance capabilities. CABI quotes a study which concluded: “Ips typographus beetles are able to fly over long distances. Wind and air movements can be additional factors enabling dispersion up to 43 km.”

Anything is possible and the UK plant health authorities may well have genetic-based or other sound evidence to support their ‘blow-over’ theory for all the infestations identified so far, but I wish they would share it with us all. In the meantime there are several facts which cause me to have nagging doubts about the ‘blow-over’ theory. Why do sequentially occurring outbreaks since 2018 show on balance an east-to-west trend across the counties south of the River Thames? 

Then there’s the case of a forester colleague on site in central Europe, who was watching contractors felling and extracting Norway spruce infested with Ips typographus and earmarked for biomass burning. When he enquired whether the wood was being burned locally he was told this harvest would be travelling much further and to his own country, the UK. 

But most of all, why should Ips typographus, which has been devastating Norway spruce across Europe for thousands of years, wait until 2023 to arrive in the UK? On that I stand to be slightly corrected because the severity of the first outbreak in Kent suggested the infestation had been festering there for up to eight years before being found – but what’s eight years when ancient records show that outbreaks were occurring in 15th-century Germany?

CAUSING COMMENT IN SCANDINAVIA AND IRELAND

The first finding of one beetle in Scotland caused considerable comment. Irish foresters, concerned for the health of their own spruce plantations, called on their government to ban imports of Scottish spruce timber. Scandinavian forest industries have been fighting this pest for centuries and know from bitter experience the timber loss and cost implications of Ips typographus. They have offered some good advice about prompt proactive measures to stop the pest gaining a foothold, as it has right across Europe wherever Norway spruce is grown.

All wood and debris from Ips typographus-affected and at-risk Norway spruce growing on the first two sites at Ashford in Kent (December 2018) were incinerated on site, although this high-end eradication measure appears to have been dropped for subsequent outbreaks (Image: Kingwell Holdings)

The Irish Forest Owners (IFO) Group delivered a strong warning about the impending disaster awaiting Ireland should this highly damaging beetle get into the country. It said: “As things stand, we import substantial quantities of logs with bark on for processing in Irish mills and much of this timber comes from Scotland.

Recently, the eight-toothed spruce bark beetle was discovered in Fife, on the east coast of Scotland, and consequently there is an increased risk associated with the importation of those logs.”

• READ MORE: Irish forest owners demand action after Ips typographus Scotland find

Comment from the Swedish forestry sector took the form of some good advice. In the spring of 2022, the Swedish Forest Agency noted that 80 per cent of the bark beetle-affected trees from 2021 were still in the forest. One of the reasons was that no tangible actions had been taken against the pest. The agency settled for information campaigns that turned out to have a limited effect on the problem. 

In the spring of 2022, Swedish forest owners prepared for a nightmare scenario following vast windthrow damage in some parts of the country. However, the summer of 2022 was wet and cold, which slowed the reproduction and spread of the bark beetle. Nevertheless, Sweden has a big problem. Each and every year millions of cubic metres of timber are damaged. It’s a war that can’t be easily won. So, it can’t be said too often that rapid reaction and action is important. That’s the message from Swedish forestry to Scotland.

FC REVEALS SOME BUT NOT ALL

Forestry Commission staff must be mind-readers, having gone some way in answering questions about Ips typographus that were nagging away at the back of my mind as I was preparing this article.

In a web posting entitled ‘Behind the Scenes at the Forestry Commission: Managing Ips typographus – five years on’, Fred Toft, the Ips typographus project manager in the plant health forestry team, shared insights into the combined work of Forest Research, the Forestry Commission and DEFRA in the management of this insect pest. 

Any attempt to rid large parts of southern England of Norway spruce will prove a tall order indeed. (Image: Stock)

The number of infestations identified since December 2018 is considerably more than I had imagined. The team has investigated more than 750 sites during the last five years but says only six per cent have returned positive identification of infestation and breeding galleries. However, that works out at 45 infestations, which more or less tallies with the 44 eradication sites specified further on in the account.

The account says that under the right conditions beetle numbers can increase to levels which cause the insects to attack healthy trees, although this has not yet been seen in the UK, they claim. However, that’s not what I understand from contractors who worked on the first pair of infestations recorded in Kent. They recall how the severity of beetle attack indicated one infestation had been festering for a number of years and that healthy Norway spruce trees were showing evidence of beetle attack. 

• READ MORE: Restrictions placed on spruce log exporting from Scotland to Ireland

Once Ips is confirmed to be breeding, the site is labelled an ‘eradication site’ and Forest Research scientists along with FC colleagues will visit to assess the severity. Currently there are 44 eradication sites (established since 2018) in the south-east of England. 

And now we return to the crux of the problem – how the beetle first arrived in the UK. Established thinking has always claimed that the most likely mode of long-distance movement, from continental Europe into the UK, was in the bark of spruce logs moved around. 

However, as mentioned above, the team is now hypothesising that UK infestation is entirely due to ‘blow over’ of adult beetles from continental Europe. The reason given was that ground surveys in 2019 and 2020 failed to find any evidence of breeding populations in the UK, although clearly that does not mean they were not there. I recall visiting a site in Essex in August 2020 where Norway spruce was devastated by bark beetles and where Ips could not be completely discounted.

Forest Research entomologists were unable to visit the site to confirm one way or the other due to COVID lockdown restrictions.

To be fair, the team says it is only a hypothesis. But I find it difficult to accept and will continue to have very strong doubts until I see hard evidence to support it.

SITKA SPRUCE IS THE END GAME

Norway spruce in southern England is essentially inconsequential within the scope of the FC’s programme of eradication. The end game is protection of the vast swathes of Sitka spruce in Scotland and Northern England. However, the FC is in bit of a quandary over Sitka spruce. Hardly any, if any, Sitka is grown in continental Europe due to the tree’s requirement for high rainfall throughout the year, which means the UK is the only European country where it is grown commercially. The native range for Sitka is western North America, but Ips is absent from there. As such, Sitka has never been put to the test against Ips, which means its susceptibility or resistance is essentially unknown. Forest Research scientists are apparently engaged in long-term research to assess this.

The UK plant-health authorities are clearly engaged in an intensive programme to manage if not eradicate Ips typographus from Norway spruce in southern England where the insect pest appears to have established. However, you can’t help suspect it also presents a serious risk of removing yet another commercial conifer species from southern and eastern England. You might say, and with some justification, that removal of Norway spruce from south-east England and East Anglia is no big deal because Norway spruce tends not to do well in these areas due to insufficient rainfall. However, you only have to go a little further west, to the Surrey Hills and West Sussex, where you will see some of the highest-yielding Norway spruce in the British Isles, and much of this on FC land.