Except for the presence of wings, the winged form of the bean aphid is similar in appearance to the wingless one. Although bean aphids do not vector viruses as efficiently as green peach aphid, generally bean aphid occurs at higher densities, which tends to negate the differences in virus transmission efficiency. Infestations of bean aphid generally begin on young leaves in the center of the crown. As the number of individuals increases, older leaves are colonized. The aphid is found mainly on the underside of leaves and only rarely on upper surfaces.
Infested leaves curl under and inward and become severely distorted.
The leaf margin and eventually the entire leaf becomes necrotic. Heavy populations may kill foliage, even in large mature plants. Bean aphid produces large amounts of honeydew and infested leaves are usually covered with sooty mold. If the aphids are killed, either by insecticides or natural enemies, leaves resprout from the crown and new foliage begins growing. The principal way of reducing virus transmission by the bean aphid is adherence to the beet-free restrictions and planting dates established by grower and processor agreement.