Pest profile

Azalea Bark Scale

Acanthococcus azaleae (formerly Eriococcus azaleae) · Hemiptera: Eriococcidae[2]

Azalea bark scale is a soft scale that forms white cottony sacs on the twigs of azaleas, rhododendrons and other shrubs, often in branch forks.[1]

No licensed photo of this species is available yet; the identification notes below describe what to look for.

How to identify it

  • Mature females are about 0.13 inch long and look like white cottony sacs on twigs and stems, especially in branch axils.[1]
  • The eggs, crawlers and adults under the whitish covering are red.[1]
  • Immature scales look superficially like mealybugs.[1]

Look-alikes

Look-alikeHow to tell them apart
MealybugsYoung azalea bark scales resemble mealybugs; look for red insects under white cottony sacs on azalea twigs.[1]

Where it lives

The PNW Insect Management Handbook covers it in Pacific Northwest landscapes, recently on blueberry as well.[1]

US map: public records from 8 states since 1990 (GBIF).

Biology and life cycle

It overwinters as an adult and lays eggs in spring; mobile crawlers move over the plant, then settle and form a protective covering.[1]

There's usually one, possibly two, generations a year.[1]

Hosts include andromeda, azalea, rhododendron, hawthorn, poplar, willow and blueberry.[1]

Damage and signs

  • The PNW handbook advises paying particular attention to sickly, low-vigor plants when inspecting for it.[1]

Health risk

It feeds on plants; the PNW Insect Management Handbook mentions no risk to people.[1]

Control

Prevention

Inspect twigs in the dormant season, use sticky tape and a 10x lens to spot red crawlers, and avoid excess nitrogen.[1]

Traps and physical control

Scrape scales off with a fingernail or toothbrush, prune off major infestations, and wrap sticky tape near adults to catch crawlers.[1]

Biological control

Beetles and parasitic wasps help control it; check under the covering for live scales and avoid broad-spectrum insecticides.[1]

Common questions

What are the white cottony things in my azalea's branch forks?
Likely azalea bark scales; the red insects live under the white sacs.[1]
When are azalea bark scales easiest to control?
As crawlers, the stage most susceptible to sprays; monitor with sticky tape and a hand lens.[1]

Sources

  1. Pacific Northwest Pest Management Handbooks (OSU, WSU, University of Idaho), “Azalea (Rhododendron): Azalea bark scale (Insect Management Handbook).” pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/azalea-rhododendron-azalea-bark-scale (accessed 2026-10-06)
  2. iNaturalist, “Acanthococcus azaleae taxon page (order and family).” www.inaturalist.org/taxa/1514559 (accessed 2026-10-06)

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