Common on arborvitae in many states, and also infests other conifers such as cedar, juniper, and cypress. Feeding on the stems and twigs can lead to dieback and discoloration of branches and foliage on infested plants, along with large amounts of honeydew on surfaces below. These are primarily cold weather aphids that may first appear on plants in late fall, become abundant in very early spring, and usually disappear from foliage when warm weather hits. It is possible that they may continue feeding on the roots of the plants.
Winter applications of dormant oils, directed to the interior of the plants so that stems and bark are coated, can kill many aphids present. A contact insecticide will also be effective, again concentrating on the stems and branches. A soil-applied systemic applied in late winter can kill the populations prior to their peak abundance in the spring.