Abstract
White spruce (Picea glauca) holds ecological and economic significance as a key conifer species in Canada. The populations of white spruce in northwestern Canada face the imminent risk of drought stress, intensified by rising temperatures linked to climate change. To address this challenge, the assisted relocation of white spruce is considered a robust conservation strategy. The proposed relocation involves transplanting drought-tolerant populations from southwestern Canada to Alberta, aiming to better adapt to the escalating drought stress. However, the repercussions of climate warming extend beyond drought stress, as they also exacerbate threats from insects and pathogens. Among these threats, the eastern spruce budworm (Choristoneura fumiferana) stands out as a significant menace to white spruce. Historically, it has led to substantial losses in white spruce populations. And the needle terpenoid concentration plays a significant role in the chemistry defense of white spruce against eastern spruce budworm. Notably, there exist substantial research gaps regarding the resistance of southeastern white spruce populations in Alberta to the eastern spruce budworm.
The aim of this study was to examine variations in terpene content in white spruce needles from diverse source locations that migrated to Alberta and assess the impact of terpenes on feeding and mortality in eastern spruce budworm larvae. This study collected foliar monoterpene and sesquiterpene concentration from white spruce trees in six populations spanning five provinces in Canada. The findings revealed that white spruce leaves from southwestern populations exhibited lower terpene levels, and the presence of terpenes resulted in reduced body weight gain and increased mortality in eastern spruce budworm larvae. Therefore, this experiment implies that the cold hardiness and susceptibility to the eastern spruce budworm of the chosen seed source should be considered in future migrations of white spruce populations. Additionally, enhancing the detection of the eastern spruce budworm is crucial when establishing populations of southeastern white spruce in Alberta. This proactive approach aims to identify outbreaks at their early stages, enabling the timely use of insecticides to mitigate damage.