Aphids are nearly transparent, softbodied sucking insects. When present in sufficient numbers, aphids can cause yellowing and premature death of leaves.

The aphids exude drops of sugary liquid known as "honeydew", which may cause tiny scorch marks on the foliage and tends to encourage the development of sooty molds. The feeding of Greenbug aphid (Schizaphis graminum) is especially damaging, resulting in the development of necrotic areas sometimes accompanied by purpling and rolling of the infested leaves. This subset identifies materials that are tolerant to greenbug aphids. J. Econ. Entomology (2003) 96: 202-206

Source: CIMMYT Wheat Germplasm Bank