Green Spruce Aphid (Elatobium abietinum)
Occasional*: True Firs, Siberian Larch, Eastern White Pine, Scotch Pine, Douglas Fir
*Only during outbreaks
The green spruce aphid is a small (1-2mm), green insect that is almost exclusively found on spruce species (Picea). Green spruce aphids are a non-native, invasive species that stunt growth by defoliating parts of the tree and can cause significant mortality outside of its native range. Feeding can be spotted in 5-10 days on Sitka spruce by yellow spots on the needles which can lead to whole needle discoloration and defoliation. The aphids generally feed on older needles and branches and avoid any new growth, so another sign of this pest is defoliation of all but the current season’s needles. On younger trees (< 5 years), the aphids primarily feed on the upper canopy, while in older trees they attack shaded areas, which are generally on the lower portion of the tree. Like many aphids, the green spruce aphid produces honeydew, which facilitates the growth of a sooty mold on the host trees’ stems. When present, this sooty mold is helpful for positively identifying the green spruce aphid. Shaking affected foliage over a piece of white paper to see if green aphids fall onto it is another common method of detection.
The local distribution of this insect is unknown, but appears to be widespread. Trees with symptoms consistent to those produced by green spruce aphids have been found along Highway 101 near Humboldt Lagoon as well as in some areas of Ferndale.
Pests and Pathogens with Similar Symptoms
Giant Conifer Aphids (Cinara spp.): Aphids in this genus feed on sap from roots, twigs, and branches of various conifer species. Although they are aphids and share a basic body plan, they are much larger than green spruce aphids (5-6 mm in length) and dark brown or black instead of green. They are also frequently mistaken for ticks, so if your aphid looks like a tick, it’s likely a giant conifer aphid and not a green spruce aphid.
Description with distribution map, aphid biology, and management strategies:
Description of the aphid. Note that risk and management sections are written for a European setting and may not be accurate to local forests and conditions :