Backyard Grapes Identify & treat grapevine problems
Insect / pest low severity

Grape erineum mite

Colomerus vitis

A microscopic blister mite that raises fuzzy welts on leaves — alarming but rarely harmful.

Grape erineum mite (Colomerus vitis) galls, leaf underside and upper side Photo: Olivier Lemoine (Photo-Terroir.fr) Wikimedia Commons CC BY-SA 4.0
Erineum mite damage on home garden grape leaves: blisters on top, concave areas beneath filled with white felt-like enlarged leaf hairs Photo: J.R. Natter OSU Extension Service Metro-area Master Gardener Newsletter
Grape leaf blister mite damage on a grapevine leaf Barmac (Amgrow)

Description

The grape erineum mite is a microscopic relative of spider mites that causes one of the most commonly misidentified symptoms in the vineyard. Its feeding makes the leaf grow blisters on top and a dense mat of felty hairs beneath — white or tan at first, then rusty red. Growers often mistake the fuzzy underside patches for downy mildew, but downy mildew’s growth wipes off and sits under yellow “oil spots”, while the erineum is a firm, felt-like mat of leaf hairs that won’t rub away.

The reassuring news is that it almost never matters. The mite disfigures leaves but rarely affects the vine’s health or crop, so on an established vine the right response is usually to do nothing. Only heavy infestations on young vines justify a sulphur or oil spray at bud swell.

What to look for

  • Raised blisters or bumps on the upper leaf surface.
  • Dense, felty white-to-tan hair (the "erineum") in matching patches on the underside.
  • Patches later turn reddish-brown; young leaves may look puckered or distorted.
  • Vigour and yield are almost never affected.

Treatment options

Cultural & prevention

Start here — habits that stop problems before they spread.

  • Usually cosmetic — no action is needed on established vines.
  • Pick off the worst leaves early in the season if the look bothers you.

Organic / low-toxicity

Gentler sprays and biologicals for active outbreaks.

  • For heavy cases on young vines, sulphur or horticultural oil at bud swell.

Conventional fungicide / pesticide

For severe cases. Always follow the product label.

  • Rarely warranted; specific miticides only if damage is genuinely severe.

Sources

This entry is based on the references below. Read them for full detail and for spray timings and rates valid where you live.

  1. Grape Erineum Mite — UC IPM
  2. Grape: Grape erineum mite — Washington State University Extension (Hortsense)
  3. Grape-Grape erineum mite — Pacific Northwest Pest Management Handbooks (OSU / WSU / U. Idaho)