A groundbreaking study focusing on Ips typographus, the bark beetle responsible for significant damage to European forestry in recent times, has shed light on its threat to the Sitka spruce. Titled ‘Investigating the threat to Sitka spruce from Ips typographus: discrimination and colonization of Britain’s principal commercial conifer by a damaging forest pest,’ the research was jointly conducted by Forest Research and Rothamsted Research, and published in the Pest Management Science journal.
Ips typographus, also known as the eight-toothed spruce bark beetle, is recognized as a severe and destructive pest primarily targeting Norway spruce tree species, capable of causing widespread tree mortality in affected forests. While the beetle typically targets stressed, weakened, or felled trees as a secondary pest, favorable environmental conditions can lead to population surges, resulting in attacks on healthy forests as well. This has raised concerns about the potential impact on commercial forestry in both Ireland and the UK.
Since 2013, over 100 million cubic meters of Norway spruce have succumbed to the eight-toothed spruce bark beetle in Europe, highlighting the scale of the devastation caused by this pest. Although the Irish government has confirmed the absence of the beetle in Ireland, its presence was detected in southeast England last year, where localized breeding populations were established. The UK government has since taken steps to eradicate these populations.
The year 2024 marked a significant milestone as the bark beetle was identified on Sitka spruce for the first time, challenging the conventional belief that it only targeted Norway spruce species. The new study revealed that the beetle shows a similar affinity for Sitka spruce as it does for Norway spruce, underscoring the potential implications for commercial forestry in the region. Dr. Daegan Inward, a Forest Research scientist and the study’s author, emphasized the importance of understanding the susceptibility of Sitka spruce to the beetle, stating that this research is a crucial step towards building that knowledge.
The research was conducted at the Forest Research quarantine containment facility in Surrey and a specialized chemical ecology lab at Rothamsted Research. The findings were further validated in a spruce forest in the Ardennes region of Belgium, which harbors an endemic population of the beetle. The study revealed that Ips typographus exhibits a similar attraction to Sitka spruce as it does to its primary host, Norway spruce, and readily selects fresh-cut Sitka spruce logs as a breeding resource.
The study also found that the odors of aged wood from both Sitka and Norway spruce were equally appealing to the bark beetle, with fresh Sitka spruce being more attractive than fresh Norway spruce. Dr. Inward highlighted that while the research advanced the understanding of cut Sitka spruce as a suitable breeding host, the defensive capabilities of live, growing trees may differ significantly. Current research efforts are focused on assessing the susceptibility of live Sitka spruce trees in European forests to bark beetle attacks.
When a tree is infested with the eight-toothed spruce bark beetle, examination of the bark and the wood beneath typically reveals a linear gallery system where females lay their eggs. This characteristic has earned the beetles the nickname ‘engraver’ beetles due to the appearance of these galleries. The ongoing research aims to provide a clearer understanding of the potential impact and risks posed by Ips typographus to Sitka spruce, and how forest management practices can address these challenges.
