Saissetia oleae (Olivier)
Common name: Mediterranean black scale.
Geographical distribution: Cosmopolitan; CIE Map #24, 1973 (revised).
Host plants: Polyphagous.
Morphology: The oval, almost flat body of the young female is 3.0-6.0 mm long and its shield is dark-brown, bearing two transverse crests and one median ridge that together form the letter H. Some populations that infest citrus may consist of scales that are yellow in their early stages, but all females become darker and very convex when ovipositing. The short, spine-like setae are sparsely located all over the dorsum of the body; antennae usually with 8 segments and the anal plates together form a quadrate, each half bearing three setae, one longer and located somewhat anteriorly to the two shorter posterior setae.
Economic importance: Damage (especially to citrus and olive trees) is due to secreting very large amounts of honeydew that is colonized by sootymold fungi, covering fruits and leaves by a thick black mass. As a result leaves drop, fruit may be reduced in quality and twigs dry up.
Life history: The pest reproduces by parthenogenesis, each female producing about 800 (and up to 2,000) eggs. The crawlers settle mostly along the main veins on the lower sides of mature citrus and olive leaves. Many young females migrate to twigs and branches later, in autumn, and remain there for the rest of their lives. Within citrus trees the pest is located mostly on the northern side. On the trees (and between adjoining trees) the crawlers disperse by walking, whereas between host plants they are wind-borne. On citrus and on unirrigated olive the scale has only a single annual generation (crawler emergence peaking in April-May). On irrigated olives two generations may annually be completed (the main crawler production being in June and in mid-winter). The pest does not undergo a winter diapause and its young stages occur on irrigated olive trees throughout the year. In the laboratory the scale can be mass-reared on potato sprouts.
Chemical control: Due to the intense activities of natural enemies, only white oil is recommended, and only in severe outbreaks. Treatments should be aimed at the susceptible young stages, because the elder scales are insensitive to this treatment. Some biopesticides of fungal origin provided satisfactory control of the pest in Egypt.
Biological control: The encyrtid endoparasitoids Diversinervus elegans and Metaphycus lounsburyi Howard, along with the coccinellid Chilocorus bipustulatus (Linnaeus) are the more important natural enemies of the pest. In Cyprus the pest was fully controlled by two introduced species of Metaphycus.
Abd-Rabou, S. 2004. The role of augmentative releases of indigenous parasitoid Metaphycus lounsburyi (Hymenoptera: Encyrtidae) in enhancing the biological control of Saissetia oleae (Homoptera: Coccidae) on olive in Egypt. Archives of Phytopathology and Plant Protection 37: 233-237.
Argov Y, Rossler Y, 1993. Biological control of the Mediterranean black scale, Saissetia oleae (Hom.: Coccidae) in Israel. Entomophaga 38: 89-100.
Ibraheem, A.M., Al-Arnaouty, S.A.G., Moussa, S.F.M. and Helmy, S.M.Y. 2012. Efficiency of certain biopesticides against the olive black scale insect, Saissetia oleae (Olivier) on olive trees at Giza Governorate, Egypt. Egyptian Academy Journal of Biologal Sciences 5: 87-93.
Mendel, Z., Podoler, H. and Rosen, D. 1982. Population dynamics of the Mediterranean black scale, Saissetia oleae (Oliv.) on citrus in Israel. 3. Occurrence of a yellow form. Journal of the Entomological Society of Southern Africa 45: 227-229.
Mendel, Z., Podoler, H. and Rosen, D. 1984. Population dynamics of the Mediterranean black scale, Saissetia oleae (Oliv.) on citrus in Israel. 5. The crawlers. Journal of the Entomological Society of Southern Africa 47: 23-34.
Orphanides, G.M. 1993. Control of Saissetia oleae (Hom., Coccoidea) in Cyprus through establishment of Metaphycus bartletti and M. helvolus (Hym., Encyrtidae). Entomophaga 38: 235-239.
Peleg, BA. 1965. Observations on life cycle of black scale Saissetia oleae Bern on citrus and olive trees in Israel. Israel Journal of Agricultural Research 15: 21-26.
Swirski, E., Wysoki, M. and Izhar, Y. 2002. Subtropical Fruits Pests in Israel. Fruit Board of Israel (in Hebrew with an English Summary).