Beech Erineum

Felt-like eriophyid mite erineum patches are now very obvious on American beech (Fagus grandifolia) in southwest Ohio. I've long identified the culprit behind the patches as Acalitus fagerinea (family Eriophyidae). However, I'm now convinced there may be two species of eriophyids that produce erineum patches on American beech.

The felt-like erineum patches produced by the eriophyid mite, Acalitus fagerinea, on the upper leaf surfaces of American beech are now appearing in southwest Ohio.  Currently, the patches are light-yellow.  However, they progress through several color stages throughout the season from light green in the spring to brilliant yellow to yellowish-gold then rusty red to reddish-brown and finally dark brown.

Although the patches are located on the upper leaf surface, they cause a dimpling of the lower leaf surface beneath the patch. 

...