Deformed grape leaves with spots underneath

Asked July 16, 2019, 11:38 AM EDT

See attached picture. This is on one of my pinot noir vines (out of 15 total). It is not on all of the leaves. I couldn't find any similar pictures when I searched for grapevine problems. I am curious what it is and what I should do to treat it. Thanks!

Washington County Oregon

1 Response

Thank you for the excellent images.

Both the white fuzz (undersides of leaves) and "blisters" (bulges top side) are caused by very tiny grape erineum mites. Later in the season, the white fuzz will become tan, then brown.

These small mites are invisible unless at least 10x magnification is used. They are elongate and have 2 pair of legs. So, they are far different than the spider mites you may be familiar with on other plants.

They do not affect production or grape quality. You can ignore them. They won't spread to other plants in your garden.