Identification
Brown Ambrosia Aphids (Uroleucon ambrosiae) are about 1/8 inch (4 mm) long. They are reddish brown to brown to dull red with two-tone black and yellow legs and black cornicles (“tail pipes”). These cornices are used to eject chemicals used in defense against some predators. Some adults have wings. These aphids suck fluids from their host plant, and eject a sweet liquid, referred to as honeydew, which is often collected by ants, which in turn protect them from some predators.
These aphids are abundant at both of our nature centers, especially later in the growing season. This species feeds on petals and leaves of a variety of flowers including black-eyed Susan (Rudbeckia), coneflower, and sunflower. Active spring and summer; it is particularly noticeable from mid to late summer.
According to one authoritative source this species appears to specialize on the giant ragweed, Ambrosia trifida. It generally does not cause damage. It could cause discoloration of flower petals and leaves, resulting in wilting if populations are high.
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