Most aphids are small, soft-bodied insects, of various colors (green, yellow, orange, red, black or white). Some may be covered with fluffy white wax. All aphids have long, slender mouthparts, which they use to suck out plant fluids. This feeding causes curling, distortion, or wilting of the leaves. Aphids excrete honeydew, which makes the leaves sticky and supports the growth of sooty mold.
Green peach aphids on the underside of a leaf. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org
Aphid infestation and honeydew on gardenia. Photo: Matthew Borden, University of Florida, Bugwood.org
Sooty mold. Photo: Joseph OBrien, USDA Forest Service, Bugwood.org
Management
Aphids have several generations a year and are generally more of a problem May through June and again in the fall. Control is often not necessary because of predator and parasite activity. Common predators are green lacewing larvae, lady beetles, hover fly larvae and predatory bugs. Several small wasps parasitize aphids. Parasitized aphids turn brown and remain on the leaves. If necessary, aphids may be reduced by washing them off infested plants with a stream of water. If damage is obvious and little predator or parasite activity is noticed, aphids may be controlled with an application of insecticidal soap.