It is smaller than your fingernail, but this hairy beetle is one of the biggest single threats to the UK’s forests.

The bark beetle has been the scourge of Europe, killing millions of spruce trees, yet the government thought it could halt its spread to the UK by checking imported wood products at ports.

But this was not their entry route of choice – they were being carried on winds straight over the English Channel.

Now, UK government scientists have been fighting back, with an unusual arsenal including sniffer dogs, drones and nuclear waste models.

They claim the UK has eradicated the beetle from at risk areas in the east and south east. But climate change could make the job even harder in the future.

The spruce bark beetle, or Ips typographus, has been munching its way through the conifer trees of Europe for decades, leaving behind a trail of destruction.

The beetles rear and feed their young under the bark of spruce trees in complex webs of interweaving tunnels called galleries.

When trees are infested with a few thousand beetles they can cope, using resin to flush the beetles out.

But for a stressed tree its natural defences are reduced and the beetles start to multiply.

“Their populations can build to a point where they can overcome the tree defences – there are millions, billions of beetles,” explained Dr Max Blake, head of tree health at the UK government’s Forest Research.

“There are so many the tree cannot deal with them, particularly when it is dry, they don’t have the resin pressure to flush the galleries.”

Since the beetle took hold in Norway over a decade ago it has been able to wipe out 100 million cubic metres of spruce, according to Rothamsted Research.

As Sitka spruce is the main tree used for timber in the UK, Dr Blake and his colleagues watched developments on continental Europe with some serious concern.

“We have 725,000 hectares of spruce alone, if this beetle was allowed to get hold of that, the destructive potential means a vast amount of that is at risk,” said Andrea Deol at Forest Research. “We valued it – and it’s a partial valuation at £2.9bn per year in Great Britain.”

There are more than 1,400 pests and diseases on the government’s plant health risk register, but Ips has been labelled “public enemy number one”.

The number of those diseases has been accelerating, according to Nick Phillips at charity The Woodland Trust.

“Predominantly, the reason for that is global trade, we’re importing wood products, trees for planting, which does sometimes bring ‘hitchhikers’ in terms of pests and disease,” he said.

Forest Research had been working with border control for years to check such products for Ips, but in 2018 made a shocking discovery in a wood in Kent.

“We found a breeding population that had been there for a few years,” explained Ms Deol.

“Later we started to pick up larger volumes of beetles in [our] traps which seemed to suggest they were arriving by other means. All of the research we have done now has indicated they are being blown over from the continent on the wind,” she added.

The team knew they had to act quickly and has been deploying a mixture of techniques that wouldn’t look out of place in a military operation.

Drones are sent up to survey hundreds of hectares of forest, looking for signs of infestation from the sky – as the beetle takes hold, the upper canopy of the tree cannot be fed nutrients and water, and begins to die off.

But next is the painstaking work of entomologists going on foot to inspect the trees themselves.

“They are looking for a needle in a haystack, sometimes looking for single beetles – to get hold of the pioneer species before they are allowed to establish,” Andrea Deol said.

In a single year her team have inspected 4,500 hectares of spruce on the public estate – just shy of 7,000 football pitches.

Such physically-demanding work is difficult to sustain and the team has been looking for some assistance from the natural and tech world alike.

When the pioneer Spruce bark beetles find a suitable host tree they release pheromones – chemical signals to attract fellow beetles and establish a colony.

But it is this strong smell, as well as the smell associated with their insect poo – frass – that makes them ideal to be found by sniffer dogs.

Early trials so far have been successful. The dogs are particularly useful for inspecting large timber stacks which can be difficult to inspect visually.

The team is also deploying cameras on their bug traps, which are now able to scan daily for the beetles and identify them in real time.

“We have [created] our own algorithm to identify the insects. We have taken about 20,000 images of Ips, other beetles and debris, which have been formally identified by entomologists, and fed it into the model,” said Dr Blake.

Some of the traps can be in difficult to access areas and previously had only been checked every week by entomologists working on the ground.

The result of this work means that the UK has been confirmed as the first country to have eradicated Ips Typographus in its controlled areas, deemed to be at risk from infestation, and which covers the south east and east England.

“What we are doing is having a positive impact and it is vital that we continue to maintain that effort, if we let our guard down we know we have got those incursion risks year on year,” said Ms Deol.

And those risks are rising. Europe has seen populations of Ips increase as they take advantage of trees stressed by the changing climate.

Europe is experiencing more extreme rainfall in winter and milder temperatures meaning there is less freezing, leaving the trees in waterlogged conditions.

This coupled with drier summers leaves them stressed and susceptible to falling in stormy weather, and this is when Ips can take hold.

With larger populations in Europe the risk of Ips colonies being carried to the UK goes up.

The team at Forest Research has been working hard to accurately predict when these incursions may occur.

“We have been doing modelling with colleagues at the University of Cambridge and the Met Office which have adapted a nuclear atmospheric dispersion model to Ips,” explained Dr Blake. “So, [the model] was originally used to look at nuclear fallout and where the winds take it, instead we are using the model to look at how far Ips goes.”

Nick Phillips at The Woodland Trust is strongly supportive of the government’s work but worries about the loss of ancient woodland – the oldest and most biologically-rich areas of forest.

Commercial spruce have long been planted next to such woods, and every time a tree hosting spruce beetle is found, it and neighbouring, sometimes ancient trees, have to be removed.

“We really want the government to maintain as much of the trees as they can, particularly the ones that aren’t affected, and then also when the trees are removed, supporting landowners to take steps to restore what’s there,” he said. “So that they’re given grants, for example, to be able to recover the woodland sites.”

The government has increased funding for woodlands in recent years but this has been focused on planting new trees.

“If we only have funding and support for the first few years of a tree’s life, but not for those woodlands that are 100 or century years old, then we’re not going to be able to deliver nature recovery and capture carbon,” he said.

Additional reporting Miho Tanaka