Pest profile

Gall and Bud Mites

Eriophyidae (eriophyid mites) · Sarcoptiformes: Eriophyidae[4]

Bladder galls on maple leaves, felty patches on viburnum and swollen ash flowers are made by eriophyid mites too small to see without magnification.[3][2]

Leaves dotted with many small raised galls caused by eriophyid mites
Leaves dotted with many small raised galls caused by eriophyid mites. (c) Katja Schulz, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • The mites are microscopic, pale, and carrot-shaped or wormlike, with two pairs of legs at the head end.[2][1]
  • They're often yellow, pinkish or white.[1]
  • Common galls include maple bladder gall, spindle galls on maple and linden, and felty erineum galls on maple, viburnum, birch and linden.[3]

Look-alikes

Look-alikeHow to tell them apart
Insect gallsGall wasps, midges, aphids and psyllids also make galls; the mites themselves are visible only with magnification.[2][3]

Where it lives

Gall-making eriophyid mites occur widely on trees, shrubs and flowers, from ash, maple and birch in Minnesota to fuchsia in California.[3][2]

US map: public records from 48 states since 1990 (GBIF).

Biology and life cycle

They spend the winter on the host plant and start feeding and forming galls in spring as buds open.[3]

Gall mites have several generations a year.[2]

Ash flower galls start green and turn brown by late summer, and can stay on the tree up to two years.[3]

Damage and signs

  • They distort, stunt and discolor leaves, shoot tips or buds, which may drop early.[1]
  • Galls seldom harm plant health, though many galls on very young plants or for years in a row can be a problem.[3][2]

Health risk

These mites feed only on plants; the sources describe no concern for people.[2][3]

Control

Prevention

Usually no control is needed; most mite galls don't seriously harm the plant.[3][2]

Sanitation

On flowers such as fuchsia, start with pest-free plants and remove infested ones, since mites feeding inside tissue are hard to reach.[1]

Pesticides

For mites that winter on the plant, horticultural oil before spring activity is the timing Minnesota Extension gives; sprays after galls form don't work.[3]

Common questions

What are the red bumps on my maple leaves?
Probably maple bladder galls, caused by eriophyid mites; they're cosmetic and need no treatment.[3]
Can I see the mites?
Not without magnification. They're microscopic and wormlike, with four legs near the head.[2][1]

Sources

  1. University of California Statewide IPM Program, “Gall and Bud Mites (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/FLOWERS/INVERT/gallmite.html (accessed 2026-10-06)
  2. University of California Statewide IPM Program, “Gall Makers (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/gallmakers.html (accessed 2026-10-06)
  3. University of Minnesota Extension, “Insect and mite galls (Yard and garden insects).” extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls (accessed 2026-10-06)
  4. iNaturalist, “Eriophyidae taxon page (order and family).” www.inaturalist.org/taxa/55584 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.