What's That Bug? does not endorse extermination

SAGEBRUSH GALL
March 9, 2010
FOUND THIS INTERESTING GALL ON SAGEBRUSH (ARTEMESIA TRIDENTATA) IS THIS THE WOOL SOWER CALLIRHYTIS SEMINATOR OR RHOPALOMYIA?
ERNIE
OKANOGAN, WASH.

Unknown Gall on Sage

Hi Ernie,
Galls, unusual growths on plants, are often caused by insects, but there might be other reasons that the plant tissue becomes distorted and produces the odd growths.  There is a nice online piece on Gall Making Insects by John A. Byers that has good information.  This is neither a Wool Sower Gall and we are not certain if this growth on sage is caused by a Midge in the genus Rhopalomyia without doing additional research.  We did find a paper online that was published by the Journal of the Kansas Entomological Society that mentions, but doesn’t picture, a Fruit Fly, Eutreta diana, that is called a Sage Stem Galling Fly.  We found the fly pictured on the Diptera Site, but again, a photo of the actual Gall produced by the fly has eluded us.

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2 Responses to Unknown Galls on Sagebrush

  1. Aariq says:

    That certainly looks like a cecidomyiid gall to me. If it is, then you can probably ID it pretty easily using Gagné’s 1989 book, The Plant-Feeding Gall Midges of North America. Galls are separated by host plant, and then have nice dichotomous keys. I just returned the book to the library or I’d do my best to ID it myself.

  2. I just looked in that book–which not only has nice dichotomous keys but is very well illustrated–and this is a good match for the gall of Rhopalomyia medusa. A fitting name, I think! (The wool sower gall, incidentally, is only found on oak.)

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