Phytoptus avellanae

Phytoptus pseudogallarum
Calycophthora avellanae
Phytoptus coryli
Phytocoptes gallarum
Phytoptus coryligallorum

Hosts: Corylus avellana, americana, maxima, tubulosa, columa (if big bud mites occur on all of these hosts, they are probably separate species!)

Relationship: Big-bud of terminal buds; enlarged buds have surfaces of scales formed into irregular protrusions

Range: Europe, CA, WA, WV

The bud gall, known as big bud, consists of an aggregation of swollen, thickened scale leaves, often containing hundreds of mites. Their feeding activities suppress the developing young leaves or inflorescences enclosed within the scales. Eventually the enlarged buds become dark and reddish brown as they mature. The mite infests filbert or hazelnut in this country and in Europe.

Eriophyes avellanae

Hosts: Corylus americana

This gall is an abortion of the terminal bud and sometimes the lateral bud or buds. The stem does not develop, and the leaves become scarcely more than scales. Subspherical, about 1 cm in diameter. On hazelnut, Corylus americana. Rather common. Similar to Phytoptus coryligallarum of Europe.

Eriophyes avellanae

Corylus
Aborted terminal or lateral buds, diameter 1/2 inch, mite, spring

Eriophyes sp.

Corylus
Buds, swollen, aborted before or slightly after opening, mite, spring