It is most common from March to May and from September through November, but infestations may persist through the summer months. Bean aphid is a dark olive green to black aphid. It is most easily confused with the cowpea aphid.
Bean aphid has a dull, mattelike appearance while cowpea aphid is shiny.
The cauda of the bean aphid has more hairs than that of the cowpea aphid and thus appears bushy. 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.