Mature adult S. oleae appear as sessile dark grey or brown-to-black lumps attached to leaf undersides and stems. The limbs of each insect are short and are hidden beneath the body, and eyes are only visible in younger specimens with pale bodies.
Early instars are difficult to distinguish from those of other species of soft scale. First-instar crawlers (0.35 mm long) and intermediate immature instars are translucent light brown, with two black eyes placed anterolaterally. Adult females lack wings; they are 2-5 mm across, approximately circular in outline, fairly flat, yellow or grey and granular in appearance initially, becoming hemispherical and dark grey or brown to black and matt with age. Adult females develop an egg-filled hollow under the body as they become increasingly convex in shape. The small, winged males are rare.
Damage: Colonies extract large quantities of sap, causing general host debilitation and build-up of sticky honeydew deposits on nearby surfaces. The honeydew may attract attendant ants. Sooty moulds grow on the sugary deposits. Badly fouled leaves may be dropped prematurely. The older insects are usually quite easy to see as dark grey or brown-to-black lumps on leaf undersides and stems.