Spruce Aphid

Order: Homoptera
Family: Aphidae
Species: Elatobium abietinum

Description: These aphids are mostly wingless, 1 to 1.5 mm long (small), olive green to very dark and pear-shaped. The head end can be yellowish green with reddish eyes. Mouthparts are the piercing/sucking type and directed straight downward, as with all aphids. Legs long and slender. Nymphs are lighter green. Eggs are yellow to reddish to dark brown or black, about 0.6 mm long and can be very difficult to scout for.

Life History: If you were to read the daily planner of a spruce aphid it would look like this: Suck plant juice, squirt honeydew, drop egg, suck plant juice, squirt honeydew, give birth and so on. Yep, that’s about all these aphids do but they do this with great proficiency and are very successful at it. What makes them a little unusual is when they do all this. The spruce aphid is also known as the winter aphid because of its peak growth in numbers during the winter and its vanishing act during the summer. Populations start to build in October through March with peak numbers in late winter and early spring. There are several generations annually. This is another exotic pest from Europe and when the spruce aphid came over, she ditched her boyfriend. In the PNW, we only have females living here. They reproduce by means of a phenomenon called parthenogenesis, which basically results in a clone of the female. They don’t need males anymore to reproduce (but good luck evolving with out genetic exchange from us males! We really are important for something!).

Damage: Sitka spruce (Picea sitchensis), Norway spruce (Picea abies), blue spruce (Picea pungens) and other ornamental and commercial spruces are attacked by this pest on North America’s Pacific coast from Alaska to California. It may occur rarely on some other conifers such as pines (Pinus spp.) and Douglas-fir (Pseudotsuga menziesii) (taken from Forestry Canada, Forest Insect and Disease Survey, Forest Pest Leaflet No. 16 4p). Aphids feed on older needles and do not move to the new growth immediately (don’t worry, they will get to it by next fall). During feeding, needles may turn discolored and eventually yellow or brown. Most aphids are found on the lower end of branches in towards the trunk and are usually concentrated low on the tree, but high infestations can occur everywhere. Needles die back and finally drop off the twig. After multiple years of defoliation, your spruce may be threatened.

Control: Damage is most noticeable by June but then it’s too late to do anything. So if you’re worried about your spruce, get out there and start scouting! How do you scout for something so small? A good way is to get a stiff piece of card stock and your hand lens. Brush two branches together over the card stock and start squinting with your hand lens. The aphids will be knocked out of the branch and onto the card stock. If you are experiencing pretty good numbers and already see damage, get out the hose and go spray down the areas with a high-pressured dose of water. This will knock them off the branch, onto the ground where they will be left for dead. If you have a real problem, make this hose-down a weekly habit starting October.

Unfortunately, this aphid has taken the high road and avoided practically every natural enemy out there. We don’t have many aphid feeders active in the winter. Late season ladybugs and early season brown lacewings might make an impact, but probably not much of one.

Temperature and weather seem to regulate this aphid species. Temperatures below 15o F can be deadly for aphids, especially if prolonged. Hope for a few early frost periods this February.

Art Antonelli had identified some resistant spruce species: Serbian spruce (Picea omorika), Oriental spruce (P. orientalis), and Japanese/tiger tail spruce (P. polita). All these can live happily in our area.

Chemical control can be successful in managing the spruce aphid when its populations are particularly abundant. Consult the PNW Insect Management Handbook for a specific recommendation. And listen to my word of warning, read the label carefully, especially if you plan on using horticultural oils to control aphids. I didn’t do this and the blue spruce I was treating didn’t look very blue after I got done with it…