| Since the 1950’s balsam woolly adelgid (BWA; Adelges piceae) has been infesting true fir species (Abiessp.) within the Northwestern United States. BWA infestations within subalpine fir (Abies lasiocarpa) stands have led to the desiccation of tree stands throughout the northern Intermountain Northwest. Currently, it is unclear how subalpine fir morphology and physiology are altered when infested by BWA. Here, we examine subalpine fir responses BWA infestations over the course of a summer in three sites across Idaho and Utah with varying infestation level. We hypothesized that water relations would decline with increasing infestation levels, over the summer and in sites with longer durations of infestation. We found that some parameters significantly declined over the summer months and many decline regardless of infestation level and site. We observed high percentages of infested seedlings, suggesting that forest regeneration in stands experiencing high mortality due to BWA could be severely limited. Key words: Adelges piceae, Abies lasiocarpa, infestation, tree morphology, tree physiology, infested seedlings |