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Diaspididae

Diaspididae

Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea.

Common name: Armored scale insects.

Geographical distribution: World-wide. This family, with about 2,500 species in 800 genera, is the largest in the superfamily Coccoidea.

Morphology: The body of the adult female is sac-like, the head, thorax and abdomen not being clearly separated. The body bears distinct dorsal gland ducts (called macroducts), which may be one- or two-barred, as well as smaller, ventral ducts (the microducts). The head (prosoma) carries the vestigial antennae and the very long, needle-like mouthparts. The thorax bears the eye spots and (in very rare cases) the atrophied legs, as well as two pairs of spiracles. The posterior abdominal segments are fused into a pygidium, whose margins carry lobes and plates, of great systematic value. The vagina is usually surrounded by genital pores, which are lacking in viviparous species (e.g. Aonidiella aurantii). The short-lived males are insect-like, the body being separated into three parts, legs, one pair of a wings, the other (hind) pair being minute. The body of females and males is covered by a variously-colored detachable shield, which usually differs between the sexes, being larger in the female. The dorsal part of the exuvium of the preceding stages is embedded within the shield. In contrast to other Coccoidea, the shield of the Diaspididae is removable (except at molt and consists of waxes and a polyphenolic polymer.

Life cycle: Females have two immature instars whereas males have four, including the the prepupa and pupa stages, which remain within the exuvium (velum) secreted by the second instar. The female lays eggs or (seldom) larviposits first instar larvae (usually called crawlers} beneath its body. The crawlers bear three pairs of legs and antennae and are the only agents of dispersal. They move about for 1-2 days and settle, remaining at the same site for the rest of their lives. After settlement they begin to feed and to secrete a shield with characteristic colors whose shape assumes the contours of the body. An elongated species [e.g. Lepidosaphes beckii constructs an elongated shield, whereas those with a rounded body (e.g. Chrysomphalus aonidum) produce a rounded shield. The first-instar female larva molts twice to become an adult, its shield growing along, attaining most of its growth during adulthood. Shield secretion ceases as the females begin to produce young. After molting to prepupa, the male ceases to feed and to secrete the shield, which is thus smaller than that of the female (and often differently colored). The adult male emerges after its pupal stage and mates, lacks functional mouth parts and dies within 1-2 days.

The females of some species remain within the exuvium of the second-instar larva and do not construct another shield. In consequence their shields are smaller and may resemble male shields. These are the so-called pupillarial scale insects (e.g. Leucaspis pusilla).

Economic importance: The Diaspididae contains many major plant pests, such as Aonidiella aurantii and Quadraspidiotus perniciosus. These scales damage plants by sucking their sap, by injecting toxins that inhibit growth and disfigure fruits (for instance: Parlatoria oleae), and by reducing the esthetic value of the commodity by their presence (e.g. C. aonidum). In the Middle East there are ca 200 species, of which about 10% are pests, with another 30% in other parts of the world.

Management:

Chemical control: Armored scale insects can be controlled with well-timed white oil sprays, which require full cover and in some cases might be phytotoxic. The pests can also be controlled with organophosphates and insect growth regulators (IGRs).

Plant resistance: Different varieties (or species) of crop plants show variable susceptibility to armored scale insects. For instance, California red scale crawlers prefer to settle on citrus species and varieties that have relatively few oil glands as compared to species with abundant glands. Such partial resistance has rarely been explored.

Biological control: Several major diaspidid pests have efficient natural enemies, mostly aphelinid parasitoids of the genera Aphytis and Encarsia. These pests include A. aurantii, C. aonidum, L. beckii, P. oleae and Q. perniciosus. In addition, many armored scale insects are attacked by Coccinellidae and by the mite Hemisarcoptes coccophagus.

Armored scale insect pests included in this compendium

Acanthomytilus sacchari

Aonidiella aurantii (California red scale)

Aonidiella orientalis (oriental scale)

Aspidiotus nerii (oleander or ivy scale)

Aulacaspis tubercularis (white mango scale)

Chrysomphalus aonidum (Florida red scale)

Chrysomphalus dictyospermi (dictyospermum scale or Morgan scale)

Diaspidiotus ostreaeformis (European fruit scale)

Diaspidiotus prunorum

Hemiberlesia lataniae (latania scale)

Lepidosaphes beckii (purple scale)

Lepidosaphes malicola (Armenian comma hard scale)

Lepidosaphes pallidula (Maskell scale insect)

Lepidosaphes tapleyi (Guava long scale)

Lepidosaphes ulmi (oystershell scale)

Leucaspis pusilla (pine scale)

Leucaspis riccae (white pine scale)

Mercetaspis halli (Hall scale)

Mycetaspis personatus (masked scale)

Parlatoria blanchardi (parlatoria date scale)

Parlatoria cinerea (grey tropical scale)

Parlatoria oleae (olive scale)

Parlatoria pergandii (chaff scale)

Parlatoria ziziphi (black parlatoria scale)

Pseudaulacaspis pentagona (white peach scale)

Quadraspidiotus perniciosus (San Jose scale)

Pestiferous species that occur in the Middle East, without so far causing serious economic damage.

Abgrallaspis cyanophylli (Signoret) (cyanophyllum scale)

Abgrallaspis degenerata (Leonardi) (degenerate scale)

Acanthomytilus intermittens (Hall)

Adiscodiaspis tamaricicola Malenoti (tamarisk scale)

Aonidia lauri (Bouche) (laurel scale)

Carulaspis minima (Targioni Tozzetti) (minute cypress scale)

Dynaspidiotus britannicus (Newstead) (holly scale)

Diaspis boisduvalii Signoret (Boisduval scale)

Diaspis echinocacti (Bouche) (cactus scale)

Duplachionaspis berlesii (Leonardi)

Epidiaspis leperii (Signoret) (Italian pear scale)

Fiorinia fioriniae (Targioni Tozzetti) (fiorinia scale)

Furchadaspis zamiae (Morgan) (cycad scale)

Hemiberlesia rapax (Comstock) (greedy scale)

Lepidosaphes conchiformis (Gmelin) (fig scale)

Lepidosaphes pistaciae Archangelskaya (yellow pistachio scale)

Lineaspis striata (Newstead) (cypress snow scale)

Melanaspis inopinata (Leonardi) (glassy scale)

Odonaspis ruthae Kotinsky (Bermuda grass scale)

Parlatoreopsis longispinus (Newstead) (Asiatic pomegranate scale)

Pinnaspis aspidistrae (Signoret) (fern scale)

Quadraspidiotus marani Zahradnik (southern pear scale; Zahradnik’s pear scale)

Quadraspidiotus pyri (Lichtenstein) (false San Jose scale)

Targionia vitis (Signoret) (Asiatic plum scale)

References

Ben-Dov, Y. and German, V. 2003. Systematic Catalogue of the Diaspididae (Armoured Scale Insects) of the World, Subfamilies Aspidiotinae, Comstockiellinae and Odonaspidinae. Intercept, Andover, UK, pp. 1112.

Ben-Dov, Y. 2012. The scale insects (Hemiptera: Coccoidea) of Israel - checklist, host plants, zoogeographical considerations and annotations on species. Israel Journal of Entomology 41-42: 21-48.

Ebstein, R. P. and Gerson, U. 1971. The non-waxy component of the armored-scale shield. Biochimica et Biophysica Acta 237: 550-555.

Miller, D.R. & Davidson, J.A. 1990. A list of the armored scale insect pests. In: Rosen, D. (ed.) Armored Scale Insects; Their Biology, Natural Enemies and Control, pp. 299-306. Elsevier, Amsterdam.

Rosen, D. (ed.) 1990. _Armored Scale Insects; Their Biology, Natural Enemies and Control. _ Elsevier, Amsterdam.

Watson, G.W. 2002 A pictorial key to important Diaspididae (Hemiptera: Coccoidea) of the world. Bollettino di Zoologia Agraria e di Bachicoltura (Milano) 33: 175-178.

Websites: https://www.google.co.il/search?q=diaspididae&biw=1280&bih=687&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBoQsARqFQoTCK6EieOwhckCFcG3FAodVQQJEA