Parlatoria oleae (Colvée)
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea, Diaspididae.
Common name: Olive scale.
Geographical distribution: From the Mediterranean Basin to Iraq, India and China, also in some South American countries and in the U.S.A. CIE Map #147, 1962.
Host plants: Over 200 plants, including apple, apricot, pear, plum and olive.
Morphology: The dorsal macroducts are two-barred. The orifices of the marginal macroducts on the pygidium are surrounded by strong sclerotized rings, and the body is oval. The olive scale can be distinguished by having 1-4 macroducts within the frame formed by the perivulvar pores (20-50 on each side), plus a few above the anterior cluster; by the external margin of its three strong lobes that are clearly notched and by having its fourth pygidial lobe in the form of a small projection. The anus is located about a third of the distance between the posterior group of perivulvar pores and the median plates. The prosoma bears 6-8 duct tubercles. The body of all stages (including the winged males) and of the eggs is violet, except shortly after molting, when it is white. The shield of the female is pale-grey, pear shaped, 1.5-2.5 mm long, somewhat convex. The dorsal exuviae of the younger stages are darker, located at one end of the female’s shield. The shield of the male is elongated, bearing at one end only the darker dorsal exuvium of the 1st-instar nymph.
Life cycle: The pest raises two annual generations in mountainous regions, three in warmer areas. During winter most of the population consists of mated females which (on deciduous trees) remain on the wooden parts of the trees. In the bi-annual population there is little overlapping of generations; the first generation emerging in April-June, the other during August to October. In the tri-annual populations the first is in April, the other two overlapping through summer and fall. The threshold of development was calculated to be at 10°C, and about 1,300 day-degrees are required for the development of one generation. The crawlers are sensitive to arid conditions. Each female has about 70 progeny, dependent on the host plant and temperature. Male crawlers settle on the leaves whereas the female crawlers prefer branches, but when fruit is available, both infest them. This preference for fruit may explain the occurrence of economic damage even when the pest population is small.
Economic importance: Heavy infestations on leaves and branches cause extensive die-back and yield reductions. The settling crawlers inject a toxin into the plant organs on which they feed, causing dark-red spots on branches, leaves and fruit. These spots remain at the site even if the scale dies and greatly detract from the fruits’ commercial value. In addition, heavy infestations cause fruit deformations. Much of the damage to apples in the mountainous regions is caused to the late varieties, which are attacked by the pest’s fall generation. The fruit of the early varieties is usually picked before the scales occur in large enough numbers. The scale forms layers of live insects covered by many layers of dead scales, which may protect them from pesticides and serve as reservoirs for next-year’s infestations.
Chemical control: The pest may be controlled by dormant oil sprays applied on the wooden parts of trees in winter, and by organophosphates or insect growth regulators in the spring, at the emergence of the first generation. The best timing for such applications requires data on the precise emergence date of the crawlers, the most sensitive stage. Optimal timing might be obtained by using a model that utilizes the cumulative day-degrees from February 15th. The model (which had been developed for pest control in the mountainous regions of Israel) predicts that the first hatch of the scale’s spring generation will occur when 184 day-degrees have accumulated from that date. In practice, and due to variations between regions and the effect of host plants, the spray should be applied a few days earlier.
Biological control: The aphelinid parasitoid Aphytis maculicornis (Masi), may kill up to 30-40% of the pest population, but does not seem to reduce the economic damage of the olive scale on apples.
Applebaum, S.W. and Rosen, D. 1964. Ecological studies on the olive scale, Parlatoria oleae, in Israel. Journal of Economic Entomology 57: 847-850.
Basheer, A.A.M., Botha, W. and Abou Tara, R. 2010. Survey of Aphytis, parasitoid species of the olive parlatoria scale insect, _Parlatoria olea_e (Clovee) (Homoptera: Diaspididae) in Southern Syria. Egyptian Journal of Pest Control 20: 111-114.
Biche, M. and and Sellami, M. 2011. Biology of Parlatoria oleae C (Homoptera, Diaspididae) in the area of Cap-Djenet (Algeria). Agriculture and Biology Journal of North America 2: 52-55.
Cohen, H. and Nestel, D. 1993. Phenology of the olive scale and percent of parasitism upon the scale in apple orchards of the Golan Heights. Hassadeh 73: 998-1000 (in Hebrew with English summary).
Huffaker, C.B., Kennett, C.E. and Finney, G.L. 1962. Biological control of olive scale, Parlatoria oleae (Colvee), in California by imported Aphytis maculicornis (Masi) (Hymenoptera: Aphelinidae). Hilgardia 32: 541-636.
Moursi, K.S., Boulbida, M.A., Abdel Fattah, R.S. and Mourad, A.K. 2013. Some ecological aspects on olive parlatoria scale, Parlatoria oleae (Colvee) infested plum and olive trees under irrigation system at Burg El-Arab area, Alexandria, Egypt. Communications in Agricultural and Applied Biological Sciences. 78: 199-207.
Pinhassi, N., Nestel, D. and Rosen, D. 1996. Oviposition and emergence of olive scale (Homoptera: Diaspididae) crawlers: regional day-degree forecasting model. Environmental Entomology 25: 1-6.
Sadeh, D. and Gerson. U. 1968. On the control of Parlatoria oleae in apple orchards in the Upper Galilee. Hassadeh 48: 819-822, 955-957 (in Hebrew).