Balsam twig aphid
Hosts: Balsam, Fraser, grand, Siberian, subalpine and white firs, Colorado and white spruce, and juniper
Evidence: Look for curling and twisting of needles (a), distortion of twigs, and presence of aphid colonies covered with white waxy material (b). Infested tips may be sticky and shiny with honeydew or black with sooty mold. In early spring, look for tiny pale (milky) green wingless stem mothers, often on needle undersides. You may detect them from the shiny drop of honeydew. In fall and winter, the tiny flattened black eggs covered with bits of whitish wax may be seen with a hand lens near buds.
Life Cycle: The balsam twig aphid, like many aphids, has an unusual and complex life history, with five distinct life stages. Twig aphids overwinter on twigs as eggs that hatch in late April or early May. First generation nymphs feed on needles near the buds, before developing into mature wingless stem mothers. These produce living young which feed on flushes of new needles. These individuals molt three times, producing and covering themselves with white waxy material after each molt. They become winged adults which can migrate to other trees. The winged forms produce the final form of aphid, males or egg-laying females. After mating, the females lay one or two eggs on the twigs.
Managment: Natural enemies, such as lady beetles and syrphid flies, help control balsam twig aphid. Look for hatched aphids when buds show green just before budbreak to determine need for control. Application of insecticides can be made in the spring around budbreak.
Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Figure b: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 78;
Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 80-81;
Martineau, R. 1984. Insects Harmful to Forest Trees. Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 95-97;
Rose, A.H. and Lindquist, O.H. 1973. Insects of Eastern Pine . Canadian Forest Service Publication 1313. p 29-30.