Aspidiotus nerii Bouché
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea, Diaspididae.
Common name: Ivy scale, oleander scale.
Geographical distribution: Cosmopolitan; possibly the most widely-spread species in the family Diaspididae.
Host plants: Polyphagous on dicotyledons, not known from monocotyledones.
Morphology: The dorsal macroducts are one-barred, slender. The body of the female is almost rounded, yellow, 1.5 mm in length. The pygidium has three rounded lobes, the median pair largest, with a basal prolongation. The anus is located midway between the median lobes and the vulva, the latter with about 20 perivulvar pores on either side. The shield is pale-yellow, round, the juvenile exuviae slightly off-center. The winged males are yellow with red spots, about 1.1 mm in length, their white shields elongated, 1.5 mm long; the exuvium of the 1st instar is placed near one end.
Life cycle: When grown on potato tubers, development (egg to egg) of ivy scale required about six weeks at 24 and 28°C, almost 13 weeks at 19°C, and it produced about 100 progeny at 24°C, during seven weeks. On jojoba in the field the pest had two prominent population peaks, in spring and in autumn, which may be overlapping. Male crawlers usually prefer lighted plant regions, different from the settlement sites of the female crawlers, which occur on the shaded parts. On jojoba female crawlers tend to prefer male plants, and scale numbers were much higher on fertilized and irrigated jojoba than on neglected plants. Improved plant conditions thus predispose jojoba to oleander scale attack. The sex pheromone of the ivy scale was isolated; it is a sesquiterpenoid pheromone, which is unique amongst scale insects. Ivy scale occurs in uniparental (parthenogenetic) and biparental (sexual) populations. In Israel the uniparental form was found only on Pittosporum undulatum Vent. (Pittosporaceae), has a different life history and its shield is darker, thus it was described as a different species (Aspidiotus paranerii Gerson).
Economic importance:In the Middle East ivy scale is a minor pest of carobs and olives, but in other Mediterranean countries, including Cyprus (but not Egypt or Israel), it attacxks olives and all species and varieties of citrus. Damage is due to sucking out plant sap, which reduces plant growth, causes leaf drop and disfigures edible fruits; infested olives have a lower oil content. Ivy scale is also very abundant on jojoba (Simmondsia chinensis) in southern Israel, but has not yet caused damage.
Horticultural control: Pruning of olive trees and of jojoba bushes decreases scale infestations because the pest tends to settle mostly in shaded areas. The reduction of male jojoba plants also decreases pest populations.
Chemical control: Summer mineral oils and organophosphate pesticides control the pest.
Biological control: The main parasitoid of the ivy scale on olive trees is the aphelinid Aphytis chilensis Howard, which attacks mostly young females on young leaves. The main predator is the coccinellid Chilocorus bipustulatus (L.).
Alexandrakis, V. and Neuenschwander, P. 1980. Le role d’Aphytis chilensis (Hym.: Aphelinidae), parasite d’Aspidiotus nerii (Hom.: Diaspididae) sur olivier en Crete. Entomophaga 25: 61-71.
Alexandrakis, V., Neuenschwander, P. and Michelakis, S. 1977. Influence d’Aspidiotus nerii Bouche (Homoptera, Diaspididae) sur la production d’olivier. Fruits 32: 412-417.
Berlinger, M.J., Segre, L., Podoler, H. and Taylor, R.A.J. 1999. Distribution and abundance of the oleander scale (Homoptera, Diaspididae) on jojoba. Journal of Economic Entomology 92: 1113-1119.
Gerson, U. and Hazan, A. 1979. A biosystematic study of Aspidiotus nerii Bouche (Homoptera: Diaspididae) with the description of one new species. Journal of Natural History 13: 275-284.
Petschen, I., Parrilla, A., Bosch, M.P., Amela, C., Botar, A.A., Camps, F. and Guerrero, A. 1999. First total synthesis of the sex pheromone of the oleander scale, Aspidiotus nerii: an unusual sesquiterpenic functionalized cyclobutane. Chemistry 5: 3299-3309.