Parlatoria blanchardi Targioni Tozzetti
Common name: Parlatoria date scale.
Geographical distribution: The Mediterranean Basin, India, Iraq, Australia, south-west USA (whence it has apparently been exterminated). CIE Map #148, 1962.
Host plants: Date palms.
Economic importance: The scale infests the rachis, pinnae and fruits of date palms. Feeding on the pinnae causes their yellowing and subsequent tree stunting. Scales disfigure the fruit they settle on, reducing its economic value.
Morphology: The dorsal macroducts are two-barred, and the orifices of the marginal macroducts on the pygidium are surrounded by weakly sclerotized rings and the body is oval. This scale has no macroducts within the frame formed by the perivulvar pores, of which there are about 15-20 on each side. It has smooth or weakly notched external margins on the pygidial lobes, and a hardly-discernible fourth lobe. The anus is located between the posterior groups of perivulvar pores. There are no duct tubercles on the prosoma, which dorsally bears a prominent eye spot placed nearly opposite the anterior spiracles. The body of all stages (including the winged males) and of the eggs is violet, except shortly after molting, when it is white. The female shield is pear shaped, consisting mostly of the brownish second-stage exuvium, which has a paler, caudal appendage, secreted by the female. The dorsal exuvium of the first stage is lighter, placed at one end of the female’s shield, from which it slightly protrudes. The shield of the male is whitish, elongated, bearing at one end the pale exuvium of the crawler.
Life cycle: The optimal conditions for the reproduction of this scale are around 24°C and relative humidity of ca 55%, being limited below 15°C and 30% RH. In Egypt and southern Israel the pest has several annual generations, in spring and autumn. Oviposition continues throughout the year, resulting in considerable overlapping of generations.
Chemical control: Applications of organophosphates along with white oil may control the pest, but many scales survive such treatments due to being hidden in the axils of pinnae and beneath the dry fibers.
Biological control: In the Middle East the pest is usually controlled by several enemies. The most important predators are Coccinellidae, such as species of Pharoscymnus, Rhyzobius and Chilocorus bipustulatus (L.). Other predators include several species of Cybocephalus (Cybocephalidae). The aphelinid ectoparasitoid Aphytis phoenicis DeBach and Rosen is another enemy of the pest. These natural enemies, unless disrupted by pesticides, mainatin P. blanchardi below its economic injury level.
Abd El-Kareim, A.I. and Awadalla, S.S. 1998. Population dynamics of the date palm scale Parlatoria blanchardi Targ. (Homoptera: Diaspididae). Journal of Agriculture Science, Mansoura University 23: 3431-3441.
Idder-Ighili, H, Idder, M.A., Doumandji-Mitiche, B. and Chenchouni H. 2015. Modeling the effects of climate on date palm scale (Parlatoria blanchardi) population dynamics during different phenological stages of life history under hot arid conditions. International Journal of Biometeorology 59: 1425-36.
Kehat, M. 1967. Some notes on the life cycle of the date palm scale, Parlatoria blanchardi Targ., in Israel. Israel Journal of Agricultural Research 17: 175-179.
Salama, H.S. 1972. On the population density and bionomics of Parlatoria blanchardi (Targ.) and Mycetaspis personatus (Comstock) (Homoptera - Coccoidea). Zeitschrift fur angewandte Entomologie 70: 403-407.