Andricus testaceipes

The cynipid gall wasp causes galls to form on Oak.  The agamic generation galls (known as Red Barnacle-galls) are usually found low on the main trunk of a smallish tree or sapling, or else on branches near the ground. They are conical and ridged, initially purplish and fleshy, later brown and hard.  

The sexual generation galls affect the buds, but have not been found in Britain. 

Taxonomy is confusing.  According to British plant galls (Redfern & Shirley 2023), Andricus testaceipes is a different species, known from the sexual galls found in leaf midribs/petioles; the asexual form of A testaceipes may be the same as the rare A rhyzomae.  

Andricus quercuscorticis forms agamic galls on the truck of oaks; they are whitish and ovoid, and the empty sockets persist

Agamic gall Adult

Where a suitable host oak is available.

The galls persist for some time after the emergence of the wasps.

See 'Description’.

Status is difficult to determine as it is not well recorded in Britain.

Status in Leicestershire and Rutland not known.