Apterae of the aphid Dysaphis aucupariae cause pseudogalls on the leaves of Wild Service-tree (Sorbus torminalis) The pseudogall is initially pale yellow green, but soon becomes tinged with red. Its form is somewhat variable, either curled from the leaf apex to the base or laterally (from the sides of the leaf inwards). The aphids, ± 2.5 mm long, are dark greyish green, powdered with copious wax.

This may not be a true gall, and other aphids may curl, roll or distort the leaves.  

Adult

Adult: Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters. 

Where Wild Service-tree (Sorbus torminalis) is occurs - (only rarely found on S. aucuparia).

In April the fundatrices of Dysaphis aucupariae stimulate the development of rolled pseudogalls on the leaves of Wild Service-tree (Sorbus torminalis).

Status in Britain is difficult to determine due to lack of records.

Status in Leicestershire and Rutland not known.

https://influentialpoints.com/Gallery/Dysaphis_aucupariae_wild_service_aphid.htm