Ireland has so far been spared the ravages of the eight-toothed spruce bark beetle, which has killed hundreds of millions of spruce across Europe in just the last decade. But the insect is now edging closer to Irish shores, posing a dire risk to the €2 billion timber industry.
While Ips typographus, the beetle’s scientific name, has historically targeted Norway spruce, scientists are now finding it may also be able to infect Sitka spruce, the most commonly grown tree in Irish forests.
And unlike other invasive insects, which come to Ireland as stowaways on cargo ships, and can thus be stopped at port, Ips is small enough to be carried along the wind, potentially travelling hundreds of kilometres by air. In the past decade, the beetle has taken hold in England, and experts warn that Ireland must now be on guard for a potential invasion.
“It can only be a matter of time before the beetle makes its way here,” says Brian Tobin, assistant professor of forestry at University College Dublin. “Spruce is the backbone of Ireland’s forest estate, and early action will be vital in any attempts at control of the spread of this very menacing threat.”
RM Block
Across Europe, there is no co-ordinated monitoring of invasive bark beetles, and experts warn the Irish Government must do more to prepare for an outbreak. Historically, the average delay between a tree pest entering the UK and entering Ireland has been a decade. Ips first arrived in Britain seven years ago, meaning the time to prepare for an Irish landing may be quickly running out.
The eight-toothed spruce bark beetle, named for the eight prominent spines protruding from its wing covers, measures just half a centimetre in length, but despite its diminutive size, it can inflict considerable damage on forests.
The beetle burrows under the bark of spruce trees to lay its eggs, and while it tends to prefer dead or damaged spruce, if its numbers grow large enough, it can infest and kill even healthy stands of trees.
To keep the beetles at bay, last year the UK banned the planting of spruce in large parts of East Anglia and southeast England, and directed landowners to cut down their spruce and replace them with other, less vulnerable trees, offering grants to those in hard-hit areas. Recently, forestry officials have also begun using drones, camera traps and sniffer dogs to spot new infestations.
Before Ips came to Britain, officials believed the English Channel would keep their forests safe. And when, in 2018, the beetle was discovered in a stand of spruce in Kent, authorities assumed they had arrived by ship. Officials felled and chipped the infected spruce to prevent any further infestation and set out traps to kill any remaining stragglers. Their response was swift and complete, they said.
And yet, in the years that followed, bark beetles continued to be found in Norway spruce at sites across southeast England and East Anglia. The recurrent and widespread infestations led officials to speculate that the insects had not, in fact, been imported by boat, but instead were continually arriving on easterly winds from across the English Channel.
To investigate, scientists set traps in beetle hotspots on the Continent and across the water along the English coastline. In Britain, they found, beetles were clustered in areas nearest outbreaks in Belgium and France, indicating they had arrived by wind. In June 2021, scientists found, particularly favourable currents had carried beetles as far as 160km inland, meaning the insects may have travelled as much as 400km in total. The findings, authors grimly concluded, showed waters separating Britain from the rest of Europe were unlikely to protect it from the pest.
[ Second Asian hornet nest found in Cork, with sighting in Dublin confirmedOpens in new window ]
Ireland, which lies less than 30km from Britain at its nearest point, must now reckon with the possibility of a future windborne invasion. More worrisome still is the discovery last year of a breeding population of Ips in dead Sitka spruce in West Sussex. While it has historically favoured Norway spruce, scientists are now finding it is equally drawn to Sitka, which covers roughly half of Irish forests. It is not yet known whether Ips can infect live Sitka spruce, but if it can, it would pose a serious challenge for growers, most of whom are farmers.
“A spruce bark beetle outbreak would cause extensive economic loss to the forest industry, but it would be farmers that would bear the brunt,” Francie Gorman, president of the Irish Farmers’ Association, said in remarks to the Oireachtas last year.
Thus far, Ips isn’t breeding in large numbers in the UK, and its ranks are only replenished by new arrivals from the Continent. Efforts at containment are working – the government recently announced that Ips had been eliminated from 13 sites – and yet beetles continue to reach further north, most recently infesting trees in Lincolnshire.
In Ireland, officials in the North and South are carrying out yearly surveys in search of the invasive species. The island has protected zone status, meaning wood from conifers grown in affected EU countries, and impacted parts of Britain, cannot be imported unless its bark has been removed. Authorities have previously intercepted Ips at port and destroyed the infected lumber, keeping the island beetle-free. A windborne incursion, however, would be much harder to stop.
“Invasive species are either going to come in by ships, which is easy to predict, or be wind dispersed,” says Jon Yearsley, who studies the spread of invasive pests at UCD.
Wind dispersal is not thought about, he adds. Irish weather officials should be studying where windborne beetles are most likely to make landfall, but unlike the UK Met Office, Met Éireann is not modelling the spread of Ips.
[ How Ireland’s forests are undergoing a revolution to boost biodiversityOpens in new window ]
The Department of Agriculture, Food and the Marine, meanwhile, sees it as “one of the most serious pest threats to Irish forestry”, according to a spokesperson, but as of yet, it has no tailored plan for how to respond in the event of an outbreak. The department says a plan “is at an advanced stage of development”.
Across Europe, bark beetles are multiplying faster and spreading farther as temperatures rise. The beetle thrives in the warm months and dies off in the winter, and the longer summers seen with climate change mean it can reproduce over multiple generations, with its ranks growing exponentially.
Modelling by Yearsley has found that southeast Ireland is particularly prone to infestation, as its comparatively warmer climate could “easily allow a population to complete one generation.” And warming could make Ireland yet more vulnerable.
“If Ips did get into Ireland, what you could see is that it is able to start reproducing earlier when you have warmer temperatures,” said Caitríona Duffy, who studied how climate change might impact the spread of bark beetles while a postdoctoral researcher at Maynooth University. Ips also prefers to infest trees that have been battered by winds or weakened by drought, she says, and warming is expected to fuel both more intense windstorms and more frequent dry spells in Ireland.
While it may be possible to contain a single infestation by felling infected trees and removing their bark, in a scenario where there are continual incursions of windborne insects, as in England, officials would need to undertake extensive surveillance and tamp down on outbreaks quickly, says Florentine Spaans, an entomologist with the Agri-Food and Biosciences Institute in Northern Ireland.
[ Ash dieback: It’s hard to ignore the lines of dead and dying trees around IrelandOpens in new window ]
“We’ve seen this with ash dieback,” she says. “If you catch it too late, you spend a lot of effort trying to contain it or eradicate it.”
Over the past decade, dieback has afflicted some 16,000 hectares of forest and is expected to wipe out at least 90 per cent of the trees in Ireland. If Ips can gain a foothold here, and is able to infect live Sitka spruce, its impact could be even more devastating, foresters warn. Ash trees comprise just 3 per cent of Irish woodlands. Together, Norway and Sitka spruce cover 48 per cent. An Ips outbreak, say the Irish Forest Owners group, “would make the ash dieback emergency look simple”.
