Oat aphid

The body of the adult is about 1.0-2.5 mm (0.039-0.097 inch) in length, orange-green to olive green or occasionally nearly black in color, and has a typical orange-red band around the cornicles.
Like all aphids, R. padi uses its piercing-sucking mouthparts to penetrate plant tissues in order to reach a vascular bundle and ingest phloem sap. Although this species can remove considerable amounts of liquid and nutrients, and strong infestations can sometimes lead to contortion of leaves, the direct effect on grain yield is generally only slight, especially if plants are young at the time of infestation. The insect causes most damage by transmitting a number of viruses, especially Barley Yellow Dwarf Virus (BYDV), for which it is the most important vector.