The minute bugs that cause these leaf galls feed alternately by generation on the roots and the growing shoots of Canyon Grape and other grape vine species. Feeding begins before the leaf has expanded by a founding female that has settled down onto the top side of the leaf. Immediately that feeding causes the leaf to deform into an inverted bowl-like cup that shelters the colonizer and her offspring. The outside of the gall is on the underside of the leaf and resembles a small pincushion. Being true bugs, the phylloxera draw plant sap through piercing-sucking mouthparts. Eventually the gall will hold many yellowish bugs.

These bugs, native to America, found there way, no doubt by inadvertent human transport, to the wine-growing areas of France where they caused considerable damage. It is the feeding on the roots that causes the heaviest damage to vines. As far as I can find these bugs have not impacted grape or wine production in Arizona.