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Photo#304198
Beech, Fagus grandifolia, leaf underside, with  eriophyid mites. - Acalitus ferrugineum

Beech, Fagus grandifolia, leaf underside, with eriophyid mites. - Acalitus ferrugineum
Cary, Hemlock Bluffs Nature Preserve, bottomlands by Swift Creek, Wake County, North Carolina, USA
May 15, 2009
I thought these were egg masses on the underside of a leaf, showing as yellowish patches on the upper sides. American Beech leaves. Widespread.
Charley Eiseman corrected me. He identifies the patches as erineum patches caused by eriophyid mites of the species Aceria ferruginea. Thank you, Charley!

Images of this individual: tag all
Beech, Fagus grandifolia, leaf underside, with  eriophyid mites. - Acalitus ferrugineum Evidence on the top of the beech leaf of eriophyid mites on the underside of the leaf. - Acalitus ferrugineum

Erineum
These are not egg masses but erineum patches caused by eriophyid mites. The species is Aceria ferruginea.

 
Is this species specific to F
Is this species specific to Fagus grandifolia. I was wondering how you knew the species. Thank

 
Yes
Nearly all gall mites and insects are specific to one plant genus (if not a single plant species).

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