A beetle responsible for devastating Norway spruce populations across Europe has been found to be equally attracted to Sitka spruce, a discovery with serious implications for the UK’s commercial forestry.

The eight-toothed European spruce bark beetle, now present in the UK, threatens Sitka spruce, which makes up 25% of Britain’s forest cover and half of its commercial forestry plantations.

Initially, researchers were uncertain whether the beetle would be as drawn to Sitka spruce as to Norway spruce.

To investigate, scientists analysed the beetles’ host selection using freshly cut spruce logs and confirmed their findings in a region where the beetle population was already established. Results showed that colonisation and breeding success were similar in both spruce species. The study also found that while aged wood from both trees was equally attractive, fresh Sitka spruce was more appealing to the beetles than fresh Norway spruce.

“Our research shows the beetle may successfully find and colonise felled or wind-snapped Sitka spruce as readily as cut Norway spruce, which may increase its establishment risk in Sitka-growing regions,” said the study lead, Dr Jozsef Vuts, a chemical ecologist at Rothamsted, one of the oldest agricultural research institutions in the world.

“Pheromone traps are currently used to monitor where the beetles are in the UK and how the outbreaks are developing. In terms of management, quick removal of felled timber or wind-damaged trees from the forest could be needed,” he added.

Since 2013, over 100 million cubic meters of Norway spruce have been destroyed by this pest across Europe. The beetles typically infest windblown, damaged, and recently felled spruce trees, rapidly increasing in number before attacking nearby healthy trees.

Overwhelming the trees’ natural defences, they also introduce pathogenic fungi, including blue-stain fungus, which weakens the trees further and accelerates widespread tree deaths.

Dr. Daegan Inward of Forest Research, a co-author of the study, emphasised the need for further investigation to assess the full extent of the beetle’s threat and its potential impact on the UK’s forests.

“The populations in continental Europe have erupted over the last 10-15 years to a really unprecedented level,” he said.

“It is a native beetle to Europe but not present in the UK until very recently. Every so often you get these outbreaks of very large populations [of the beetle] that essentially shift the beetle from being a minor pest of felled material or storm damage material to the point where they can actually start attacking live healthy trees, and this is what we are seeing on the continent.

“We’re developing experiments where we are going to precipitate attacks of beetles on to these trees for direct comparison to see how the two spruce species defend themselves against the beetle.”