We are seeing hundreds of mature Sitka spruce along the coast showing signs of stress and significant needle loss. These symptoms do not necessarily mean your tree is dying, and are almost certainly caused by spruce aphids.
Spruce aphid infestations typically occur on a three-year cycle. A hard frost kills them and minimum tree mortality occurs, however that has not been the case on the North Oregon and Southwestern Washington coast. Repeated years of spruce aphid infestation have left our trees stressed, and unable to properly to defend against the aphids.
Additionally, three years of drought summers have severely weakened the trees, and recovery may not be possible for some trees, which are in severe decline. The spruce aphid is a destructive insect, especially for Sitka spruce.
Damage to the needles becomes apparent in April, May or June. When damage becomes severe enough to demand attention, aphid numbers are much lower than they were during the early season, and most of the damage has been done. Exact reasons for aphid decline in late spring are not known.
This year is by far the worst we have seen in decades. We are still urging many homeowners not to cut down trees which look brown, may be losing needles, or appear dead. At this point your trees may still be preservable. We always encourage homeowners to preserve any tree which can be saved.
International Society of Arboriculture certified arborist, certified master arborist