Found feeding on the upper stems of trees, causing stunted terminals and needle yellowing
Typically attended by ants
Typically congregating in large colonies
More difficult to find because they spread out
Often feed on 1-year-old foliage on branches; as damage progresses, foliage may yellow and appear shiny from honeydew
Ants seldom present
Where to Look
Randomly in the field
Black “soot” in leaders
Areas with yellow jackets
Similar Symptoms As
C. abietis (Giant conifer aphid) can feed throughout the year; damage may be evident any time of year. Scout for aphids in the internodal openings along the upper leaders.
C. occidentalis attracts wasps and yellow jackets in the summer as the honeydew becomes more prolific. Look for damaged foliage and black soot on the ground throughout the year. These aphids are harder to spot and are dispersed along branches.
C. abietis (Giant conifer aphid): Control using localized treatments, including crushing colonies by hand.
C. occidentalis: Control early to avoid significant foliage damage. Use labeled insecticides for spot treatments to protect populations of natural predators.