The powdery mildew Erysiphe euonymi affects our native Spindle and other non-native Euonymus.  Small orange, brown or black spheres may be seen - these are chasmosthecia which contain the ascospores (sexual or teleomorph state).

This is the only powdery mildew known to affect the native British Spindle, but Erysiphe euonymicola affects some non-native species such as the evergreen E fortunei, E nanus and E japonicus. 

host/native Spindle non-native spindle

Photograph on host plant, and add host species to the comments for your record.  If you are recording it on a non-native Spindle, microscopic examination or verification by an expert before submission to NatureSpot is recommended.

On spindles, including the native Euonymus europaeus and some non-native species.