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Home » Guide » Arthropods (Arthropoda) » Chelicerates (Chelicerata) » Arachnids (Arachnida) » Mites and Ticks (Acari) » Acariformes » Trombidiformes » Prostigs (Prostigmata) » Eleutherengona » Raphignathina » Eriophyoidea » Gall mites (Eriophyidae)
Photo#1700315
gall on beech?
Copyright © 2019 sue muller

gall on beech?
Columbia, Howard County, Maryland, USA
July 25, 2019
There were a lot of these little bumps on several leaves of American Beech. Gall? Mite??
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Contributed by sue muller on 26 July, 2019 - 8:52pm
Last updated 3 August, 2019 - 9:56am

Moved
Moved from ID Request.
… John F. Carr, 3 August, 2019 - 9:56am login or register to post comments

Probably Eriophyid mites
Extremely tiny (~100 microns); a slide mount and view under a compound microscope would be necessary to see anything. They tend to be highly host specific; accurate id of the host can often give you the answer.
… tenebboy, 1 August, 2019 - 7:21pm login or register to post comments

 
gall on beech
Hi,
You mentioned accurate host ID can often give the ID as many mites are host specific. I am positive this was American Beech. Is there a mite specific to American Beech??
Sue
… sue muller, 25 August, 2019 - 6:17pm login or register to post comments

 
Acalitus ferrugineum
The mite specific to American Beech is Acalitus ferrugineum
… Adam Kranz, 22 February, 2020 - 11:16am login or register to post comments

 
Pouch galls
These are pouch galls on the leaf. A. ferrugineum produces an erineum like this:
… Edward L. Ruden, 19 December, 2021 - 7:55pm login or register to post comments

 
Other side
The erineum is on the lower face of the leaf. It's very common for erineum galls to have this structure, with a smooth blistered spot on one side and a carpet of erineum on the other.
… Adam Kranz, 20 December, 2021 - 12:47am login or register to post comments

 
Erineum on top too
Yes, I have seen this for species such as Aceria negundi:

However, leaf top images of Acalitus ferrugineum on BG show that erineum appears on the top too:

The subject gall bulge tops are smooth. Baker et al 1996 (1) describes 3 other eriophyid species on Fagus grandifolia (American beech) leaves, but they reportedly cause no damage. This is likely an undescribed species, or a undescribed host or gall structure of a described species. This happens a lot for Eriophyidae.
… Edward L. Ruden, 20 December, 2021 - 11:42am login or register to post comments

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