The Walnut Blister Mite (Aceria tristriata) produces small blister like galls on the leaves of Walnut which often turn red.  When a tree is severely affected the fruits may become galled as well.

Gall Adult

Gall: Please provide photographs of the gall, showing both upper and lower surfaces of the leaf.  Please also state the host species in the ‘comments’ section when submitting your record.

Galls may be found wherever Walnut trees occur.

When the host trees are in leaf.

True status in Britain is difficult to determine due to lack of records.

Status in Leicestershire and Rutland not known.