Young plants may be killed or their growth checked if there is sufficient feeding by the banana aphid. However, direct damage by this aphid is generally negligible. Like many other soft bodied insects, such as leafhoppers, mealybugs, and soft scales, aphids excrete honeydew. This sweet and watery excrement if fed on by bees, wasps, ants and other insects. The honeydew serves as a medium on which a sooty fungus, called sooty mold, grows.
Sooty mold blackens the leaf, decreases photosynthetic activity, and decreases vigor of the host.
Aphids vector many plant diseases that cause substantially greater losses than that caused by direct feeding injury. This is often the most damaging feature of an aphid infestation. In nonpersistent transmission, the virus reproduces in the plant, and aphids simply aid in transporting the virus. With these types of virus-vector associations, the aphid acquires the virus and is only able to transmit the virus temporarily. Once all the infective charge is reduced by feeding or the passing of time, the aphid is unable to transmit the virus until it feeds on infected tissue again.