Conifer Aphids
Young trees of a certain size or in considerable shade are most vulnerable to infection by adelgids such as Adelges cooleyi. Mature trees are more resistant.
The coniferous root aphid, Pachypappa tremulae, previously called Rhizomaria piceae, has been a pest at several British Columbia nurseries, particularly near Prince George. This aphid has taken advantage of potted seedlings.5
The balsam woolly aphid has become established in British Columbia and can seriously damage all true firs. Quarantines have to be respected to prevent its spread.
Read more about this topic: Gall Adelgid