Acari: Eriophyoidea - gall mite Cecidophyes vermiformis Gall on Corylus avellana, Hazel Hosts: Corylus It is thought there are probably two species causing bud galls on Hazel; Phytoptus avellanae forming galls over winter and the galls of Cecidophyopsis vermiformis developing in spring and early summer. However some authorities consider that Cecidophyes vermiformis is just an iniquiline of Phytoptus avellanae

Cecidophyes vermiformis
Pamphill, Dorset. May 2018