Mercetaspis halli (Green)
(Also known as Nilotaspis halli Green)
Common name: Hall scale.
Geographical distribution: The scale is widely distributed in the Mediterranean basin, Iraq, Iran and the southern Russian republics, and has also invaded the USA, whence it had been eradicated.
Host plants: Many perennial Rosaceae.
Morphology: The dorsal macroducts are two-barred, with four pairs of marginal macroducts on each side of the pygidium. The anal and pre-anal segments carry a row of transverse macroducts. There is only a single pair of strong medial pygidial lobes and it bears a median point. There are no perivulvar pores, and the anus is located above the vulva. The elongated body of the female and all its stages are yellow. The shield of the female is whitish, elongated, about 1.0-1.2 mm long, pear shaped and with the color of chaff. 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, whitish, bearing at one end the darker shield of the crawler.
Life history: The Hall scale is viviparous, its crawlers often preferring to settle in and around young host buds, especially near the branch. The pest infests all above-ground parts of the host plants, overwintering as mated females on the bark and branches. The pest has three annual generations (April-June; July-August; September-October), the winter population consisting of mated females.
Economic importance: The pest infests above-ground parts of stone fruit trees, especially almonds, peaches and nectarines. Crawlers that settle on the fruit do not develop beyond the second stage but their feeding wounds cause pits that may remain undetected until the fruit ripens. The market price of fruit with a few reddish blemishes is often reduced. Large populations that settle on the twigs may cause their die-back.
Monitoring: Band traps, which consist of a black cloth strip fixed with a wire around young twigs between the 4th and 5th buds, provided a good indication of pest densities on buds.
Chemical control: As the main damage is caused by the first-generation crawlers that infest fruit in the spring, control efforts should be aimed at reducing the winter populations. A single application of winter oils, combined with organophosphates applied on the bark, reduced damaged to early as well as late peach varieties.
Berlinger, M.J., Dahan, R., Ben-Dov, Y. and Cohen, M. 1984. The phenology, distribution and control in Israel of the Hall scale, Nilotaspis halli (Green) (Homoptera: Diaspididae). Hassadeh 64: 722-725 (in Hebrew with an English Summary).
Berlinger, M.J., Fallek, C., Dahan, R. and Friedlender, M. 1996. Host-plant relations of the Hall scale (Homoptera: Diaspididae) on peaches and nectarines in Israel. Journal of Economic Entomology 89: 1453-1459.
Bolu, H., Gencer, L. and Özgen, Y. 2006. Infestation rates and natural enemies of Mercetaspis halli (Green) (Homoptera: Diaspididae) with new records from Turkey. Journal of the Entomological Research Society 8: 1-5.
Fallek, C. 1988. The Hall scale (Nilotaspis halli Green) on peaches and nectarines. Hassadeh 69: 270-271 (in Hebrew with an English Summary).
Fallek, C. Yablonka, G., Dahan, R., Mordechai, S. and Berlinger, M.J. 1988. Winter sprays to control the Hall scale and the olive scale (Diaspididae) on deciduous fruit trees in Israel. Hassadeh 69: 454-455 (in Hebrew with an English Summary).
Fosen, B.H., Cressman, A.W. and Armitage, H.M. 1953. The Hall scale eradication project. US Department of Agriculture, Circular 920.