Damage to the crown and buds is more obvious. Enlarged and contorted stems and twigs stand out from the healthy ones as foliage dies out. Buds are killed or growth is inhibited by the adelgids, and as old needles are shed they are not replaced by new growth. As a result, the tree becomes increasingly thin. This type of damage may persist for many years before the tree dies.
Damage also differs in regards to the tree species being attacked.
Stem attacks on subalpine and Pacific silver firs may begin at 20-40 feet above ground and then move downward. The foliage in this case becomes yellow and turns red when the tree dies. The crown of grand fir becomes darker and thinner. The leader will often curl and later break off, leaving a flattened crown. Stem attack on the grand fir starts near the base of the trunk and moves upward.