The olive scale, Saissetia oleae, is a cosmopolitan pest of citrus and olives and occurs widely in tropical regions and in greenhouses throughout the world. It is a severe pest in coffee and citrus. Many ornamental crops can also be affected.
Life cycle and appearance of Olive scale
Young females are oval, 3-6 mm long and almost flat. Their shield is dark grey or brown to black and has two transverse crests and one median ridge that together form the letter H. On citrus, early stages might be yellow but they become darker later. First-instar crawlers (0.35 mm long) and intermediate immature instars are translucent light brown.
Olive scales reproduce by parthenogenesis. Eggs are protected under the shield until they hatch. The emerging crawlers settle mostly along the main veins on the lower sides of mature leaves. Many young females migrate to twigs and branches later and remain there for the rest of their lives.
Olive scales produce large amounts of honeydew causing build-up of sticky deposits on nearby surfaces. The honeydew may attract attendant ants and sooty moulds grow on the sugary deposits. Removal of large quantities of sap debilitate the plant and can cause wilting, desiccation of tissues and dieback.