Balsam Twig Aphid
Egg-The brown eggs are covered with small, white rods of wax. They are laid in crevices in the bark.
Nymph-The nymphs are small, pale yellowish-green, wingless aphids. Nymphs that develop into egg-laying adults are slender.
Host Plants -This aphid feeds on a wide variety of hosts, including balsam, Siberian, alpine, and Fraser firs; white spruce; and juniper.
Damage -Balsam twig aphids cause curled needles and roughened bark of infested Fraser firs (Color Plate 1H). Although trees may tolerate large populations, eventually they will decline in vigor. Most serious damage occurs in Christmas tree plantations, where appearance and market value of infested trees are degraded and reduced.
Life History -Balsam twig aphids are unique pests because of their confusing life cycle and short feeding time. Each generation is different from its parent generation, and only one generation each year lays eggs. Most of the year is spent in the egg stage in crevices of the bark. The eggs are laid in early summer, and they remain on the tree throughout the fall and winter. In early spring the eggs hatch and the first generation of nymphs develops into wingless aphids called stem mothers (fundatrices). The stem mothers give birth to live nymphs, which may develop into wingless forms called fundagenae or winged forms called sexuparae. The egg-laying adults (sexuales) are winged and are the offspring of either the fundagenae or sexuparae. All of this happens in the spring and early sum mer. By the end of June, the eggs have been laid and the adult aphids have disappeared.
Control of balsam twig aphids is difficult because the damage occurs in early spring when weather is unpredictable. For specific chemical controls, see the current state extension service recommendations.