Have you seen galls on the leaves of any of your vines?  If the infestation is severe the leaves can become pretty contorted (see image).  The galls are caused by insects called phylloxera.  These insects seem to prefer certain cultivars more than others, often american or hybrids more so that vinifera.  Even though the manifestation of the insect presence is seen now, there is nothing to be done about it this time of year.  Control must take place much earlier in the season.  Dr. Rebek lists the control options as Admire Pro (imidacloprid), Assail (acetamiprid), Danitol (fenpropathrin), Movento (spirotetramat), and Surround (kaolin clay; this is a chalky barrier).  Think right about the time of bloom for control next year.

Thanks to Les Heisterberg for the photo.