Pest profile

Black Scale

Saissetia oleae · Hemiptera: Coccidae[3]

Black scale is one of California's most damaging soft scales, and its honeydew coats olive, citrus and many shrubs with black sooty mold.[1]

Several dark brown to black, dome-shaped black scales clustered on a green twig
Several dark brown to black, dome-shaped black scales clustered on a green twig. (c) Mike Bowie, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Adult females are dark brown to black, convex, up to 1/5 inch long, with a distinctive H-shaped ridge on the back.[1]
  • Crawlers are pale yellow to light brown and only 1/64 inch long.[1]
  • Infestations bring sticky honeydew and black sooty mold.[1]

Look-alikes

Look-alikeHow to tell them apart
Cottony cushion scaleA different scale with a white fluted egg sac rather than a dark H-ridged shell.[1][2]

Where it lives

Native to southern Africa, it occurs in the southern and western United States; hosts include olive, citrus, oleander, privet, rose, pistachio and many more.[1]

US map: public records from 4 states since 1990 (GBIF).

Biology and life cycle

There are two generations a year on the California coast and one inland.[1]

Females don't need to mate and may produce over 2,000 eggs under their bodies.[1]

It's more common on the coast and in dense canopies, where nymphs escape hot, dry conditions.[1]

Damage and signs

  • Sap feeding and heavy honeydew with sooty mold weaken plants and foul leaves.[1]

Health risk

It feeds on plants; UC IPM mentions no risk to people.[1]

Control

Traps and physical control

Thin dense canopies to remove the cool, humid conditions young scales need, and prune out infested branches.[1]

Biological control

Tiny parasitic wasps such as Scutellista caerulea and Metaphycus helvolus control it in coastal and northern areas; look for exit holes.[1]

Pesticides

If populations are high and parasitism low, a narrow-range oil timed to the crawler stage helps; test first for plant damage.[1]

Common questions

What is the black, H-marked scale on my olive tree?
It's black scale; the H-shaped ridge on the female is its trademark.[1]
When does oil work best?
At the crawler stage, so monitor the population before spraying.[1]

Sources

  1. University of California Statewide IPM Program, “Pest Notes: Black Scale (Publication 74160).” ipm.ucanr.edu/PMG/PESTNOTES/pn74160.html (accessed 2026-10-06)
  2. University of California Statewide IPM Program, “Pest Notes: Cottony Cushion Scale (Publication 7410).” ipm.ucanr.edu/PMG/PESTNOTES/pn7410.html (accessed 2026-10-06)
  3. iNaturalist, “Saissetia oleae taxon page (order and family).” www.inaturalist.org/taxa/396652 (accessed 2026-10-06)

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