Strange Gall on Grape Vine

Earlier this year I found a strange growth occurring on a grape vine in my yard.  It looked like a nut coming from the bud.  It was hard and woody.  Having seen similar things on other plants, I had an idea that an insect caused this phenomenon.  After asking colleagues about it and doing some research, we whittled it down to Schizomyia vitiscoryloides.  It is in the same Family as gall midges.  It is in the Order Diptera, along with gnats, mosquitoes,and true flies.  In this case, it appears the egg was laid in or near the bud.  The plant responds with unusual growth around the larva that develop from the egg.  Inside, the larva is protected and can feed.  The larva eventually falls to the ground where it will pupate.  Removal of the galls is not usually necessary, but it may help reduce future populations.  See the photos below for the gall and the inside of the gall with the yellow-colored larva.

Gall on grape vine

Gall on grape vine

Inside of the gall, with the larvae

Inside of the gall, with the larva


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