The spread of bark beetle could have a major impact on the UK’s forestry industry and cause significant ecological damage, particularly in Scotland where around 75% of spruce trees in Britain are grown. Researchers from the University of Cambridge in collaboration with Forest Research have been supporting the UK government’s efforts to understand and limit the beetle’s spread.
The eight-toothed spruce bark beetle, Ips typographus, is a major forest pest in mainland Europe. Until recently the UK was considered a pest-free area. When the first UK infestation was discovered in 2018 it led to an urgent need to understand if the beetle could become established and how far it could spread across the British Isles.
Rapid analysis supports control and monitoring
Investigators from Cambridge’s Epidemiology and Modelling group used models adapted from continental Europe to predict the impact of past, current and future climate conditions on the beetle’s lifecycle in the UK.
The research was published in the journal Plants, People, Planet on 20 October 2024.
By providing information on how many generations can breed each year and when the beetles are likely to swarm, these models play a key role in helping to monitor and control the pest.
Climate change will make UK more vulnerable to infestation
The team found that the current climate in central and southern England is warm enough to support two generations of the beetle a year. Whereas cooler temperatures further north and at higher altitudes in Scotland make it harder for the beetle to thrive.
However, the models predict that Scottish forests will become more vulnerable to beetle infestation with climate warming over time. In the worst-case scenarios for the impact of global warming on UK temperatures, two generations of the beetle could be possible throughout Scotland by 2034.
Dr Cerian Webb, Postdoctoral Research Associate in the Epidemiology and Modelling group and co-author of the paper, said “Working closely with Forest Research has ensured our models are firmly grounded in real-world applications while also guiding future data needs. This integration of modelling, fieldwork, and policy development enhances the impact of our work, informing effective surveillance and targeted control strategies for the UK Department for Environment, Food and Rural Affairs (DEFRA).”
Other environmental factors
One question that remains unanswered is why the beetle did not establish in the UK before 2018. In the 1940s large numbers of beetles were found on spruce arriving from Germany for processing in British sawmills, but follow-up surveys found no evidence of breeding in the UK.
Models using historical weather data showed that temperatures would have been warm enough to support two generations of the beetle in southern and central England at that time. This indicates that other environmental factors are at play.
Woodland area in the UK has more than doubled since the 1940s, potentially increasing the chance of beetles finding a suitable host.
The main species of spruce grown in the UK is Sitka spruce (Picea sitchensis) compared with Norway spruce (Picea abies) in continental Europe. It is possible that Sitka spruce is less vulnerable to beetle infestation, although the recent finding of beetles breeding in fallen Sitka spruce highlights the need for continued surveillance and removal.
Another factor for further investigation is the role of drought. Research shows that trees weakened by storm damage or drought are most likely to be attacked by the beetle. Climate change could lead to an increase in drought-stressed Sitka which is just as likely to be attacked as drought-stressed Norway spruce.
Next steps
One hypothesis for further exploration is whether beetles found in the UK did not breed locally but crossed the channel in wind-assisted flights. The team are now looking at the impact of this potential wind dispersal combined with existing models to refine predictions about how and where the beetle could establish in the UK.
Either way, effective surveillance is crucial to reduce the damaging impact of the beetle could have on UK forests. If the pest is allowed to settle in the UK, there is an increased chance that it could adapt to the milder climate and disperse widely across mainland Britain.
Current UK government strategy is to eradicate any breeding populations to reduce the risk of further spread, and in October 2024 the UK Forestry Commission announced a ban on spruce tree planting in parts of East Anglia and South East England.
This work was supported by the UK Government Department for Environment, Food and Rural Affairs, Forestry Commission England, and Forest Research.
Reference: Webb CR, Blake M, Gilligan CA; Phenology of the spruce bark beetle Ips typographus in the UK under past, current and future climate conditions; Plants People Planet, October 2024; https://doi.org/10.1002/ppp3.10583
Image: Forest destruction caused by European spruce bark beetle
About Plants, People, Planet
Plants, People, Planet is a multi-disciplinary Open Access journal, owned by the New Phytologist Foundation and published by Wiley. The journal publishes outstanding plant-based research in its broadest sense and celebrates everything new, innovative and exciting in plant-focused research that is relevant to society and people's daily lives. The New Phytologist Foundation is an independent, not-for-profit organisation dedicated to the promotion of plant science.