The lot we recently purchased has a massive (8-10" diameter) grapevine on it. It had grown and covered a dead tree next to it and the vine is now covered with leaves and setting fruit. However, it has the strangest growths on its leaves and stems - shiney, raised, ruby-red growths. The ends of some stems end in these pea-shaped growths.
Does anyone have any idea what this could be? I researched grape diseases on the internet and it doesn't look like anthracnose - much less powdery mildew or anything else.
Grape tumid gallmaker. A small fly by this name lays its egg within an unfolding bud or shoot tip. Maggot-like larvae hatch and feed on vine tissue. A small (1/8-1/4") reddish gall forms around the larvae as it feeds. Galls can be found on leaf undersides, clusters, and petioles. Although vineyards in New England have reported serious infestations of this pest, it has not been a problem on Long Island. Treatment is not recommended, except in extreme situations