Poplar vagabond aphid
Aspen, Cottonwood and Poplar
Appearance and Life Cycle
The aphid varies in size (0.5-4 mm in length) and colour throughout the five known generations. In May, the eggs hatch into wingless, parthenogenetic (can reproduce without mating) females on poplar trees. The nymphs begin feeding on developing buds causing the formation of galls. By mid-June, the wingless, parthenogenetic females are fully developed and give birth to a generation of winged, parthenogenetic females. These females migrate to an unknown, secondary host and give birth to a generation of wingless, parthenogenetic females. The wingless females give birth to a generation of winged, parthenogenetic females which return to the poplar tree between mid-September and mid-October. The winged females locate and accumulate in galls made by previous generations and give birth to sexually reproductive male and female aphids. After mating, the females deposit one overwintering egg inside the old galls, completing the life cycle. Because of the unique life cycle of the aphid, certain trees are infested yearly, while nearby trees of the same species remain uninfested.
The feeding action of the aphids on the terminal buds causes the formation of convoluted, bladder-like galls. These hollow galls may occur singly or in clusters of three to five, reaching up to 12.5 cm in diameter. The galls are green at first, turning woody and black in midsummer, remaining on the trees throughout the winter as unsightly growths. The galls are mainly confined to the upper one third of the tree, making them nearly impossible to prune out.
Control is not required, since the galls cause no serious injury to the tree. If the galls are accessible, they should be removed and destroyed in late fall or early spring.
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