Gall Update | Backyard and Beyond

Gall Update

Published September 17, 2021 Uncategorized 1 Comment

Zopheroteras guttatum on Quercus texana. Nutall oak has a common name, but the tiny wasp that commandeered the tree’s chemistry to induce this structure doesn’t.

Under 2mm in size, but flamboyantly patterned. Inside is the larval wasp.

Here’s another species on the same tree: Furry Oak Leaf Gall Wasp (Callirhytis furva)..

And another: Oak Leaf Gall Midge (Polystepha pilulae). This one is induced by a midge, not a wasp.

Lobed Oak Gall Wasp (Andricus quercusstrobilanus) on swamp white oak (Q. bicolor). One of the biggest of the 39 species of Cynipid gall wasps seen within 2.5 miles of my Brooklyn home. (Although these can be much smaller on other swamp whites here.) This one is a stem gall; the others here are leaf galls.

Many of these galls are detachable; they fall of their own accord. With autumn approaching, others will come down the ground as the whole leaf falls.

The larval wasp, or midge or mite, gets protection and food from these structures. What, one wonders, does the tree get out of this? Well, they do contain and isolate the pest away from the main body of the plant. Is that so galling?

1 Response to “Gall Update”

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1 TasView (Tone) September 17, 2021 at 7:18 am

Great photos and info, something new learnt today, thanks 😊

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