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White Prunicola Scale

Pseudaulacaspis prunicola[3]

White prunicola scale is a non-native armored scale that coats the twigs and branches of cherry laurel, flowering cherry, lilac and privet with tiny white covers, giving stems a snowy look and causing decline and dieback.[1][2]

Group
Insect
Order
Hemiptera
Family
Diaspididae
Sources
3 cited
Updated
2026-10-16
White prunicola scale covers scattered on a woody stem
White prunicola scale covers scattered on a woody stem. (c) Andrew Conboy, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Female covers are round, white with a yellow center and about 1/16 inch across; male covers are small, elongate and white and cluster in snowy masses under branches.[1][2]
  • Crawlers are salmon colored.[1]
  • It cannot be told apart from white peach scale in the field; it takes a microscope.[1][2]

Look-alikes

Look-alikeHow to tell them apart
White peach scaleIdentical in the field; white prunicola scale is the more likely one on cherry, lilac and privet in the Northeast, while white peach scale is more tropical and subtropical with a much wider host list.[1][2]

Where it lives

A temperate species common in Maryland and New England.[1][2]

Biology and life cycle

There are three generations a year in Maryland, with first crawlers around 513 degree days (peak bloom of tulip poplar) and the second around 1,637 degree days (after golden raintree peaks, before rose-of-Sharon is in full bloom).[1]

Crawlers can be monitored with electrical tape wrapped sticky side out around branches.[2]

All stages stay on the bark of twigs, branches and trunks year-round.[1][2]

Damage and signs

  • Preferred hosts are cherry laurel and other Prunus, Japanese flowering cherry, lilac and privet; it also turns up on holly and boxwood (UMD counts 16 plant families, UMass 18).[1][2]
  • Infestations start on outer, smaller branches and cause yellowing, leaf drop, stunting and, when heavy, branch death.[1]

Health risk

None to people or pets.[1][2]

Control

Traps and physical control

On small plants, gently scrub scales off with a soft brush; pruning is hard because it colonizes trunks and larger branches.[2]

Pesticides

Horticultural oil and sprays timed to the crawler stage give the best control.[1][2]

Common questions

What is the white crust on my cherry laurel and lilac stems?
Often white prunicola scale.[1][2]
Is it white peach scale?
They look identical in the field; on cherry, lilac and privet in the Northeast it is more likely white prunicola scale.[1][2]
When should I treat?
When crawlers hatch, about three times a year in Maryland, starting around tulip poplar bloom.[1]

Sources

  1. University of Maryland Extension (Home & Garden Information Center), “White Prunicola Scale (Home & Garden Information Center).” extension.umd.edu/resource/white-prunicola-scale (accessed 2026-10-16)
  2. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Pseudaulacaspis prunicola, White Prunicola Scale (Landscape Insect & Mite Guide).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/pseudaulacaspis-prunicola (accessed 2026-10-16)
  3. iNaturalist, “Pseudaulacaspis prunicola taxon page (order and family).” www.inaturalist.org/taxa/1007739 (accessed 2026-10-06)

Updated 2026-10-16. Built from sourced records. Spot an error? Tell us.