1.2 to 2.4 mm, dark green or greyish and globular in shape. Adult Rhopalosiphum padi (apterae) have a coating of mealy wax and live in a rolled leaf gall on their primary host Bird Cherry.

Wherever the host species occur.

Most likely to be found on Bird Cherry in late April and May.

Primary host: Bird Cherry (Prunus padus). Secondary hosts: Poaceae especially cultivated Wheat Barley and Maize as well as wild grasses. The eggs of Rhopalosiphum padi are laid on Bird Cherry in autumn in the narrow gap between the axillary buds and the stem.

Status in Britain is difficult to determine as this species is not well recorded but it is thought to be fairly frequent.

Status in Leicestershire and Rutland not known.

https://influentialpoints.com/Gallery/Rhopalosiphum_padi_Bird_cherry-oat_aphid.htm