(Newstead, 1894)
Diagnosis
Scale cover of adult female in life 1.5-2.6 mm diameter, circular to oval, flat, off-white to pale brown or yellow, with yellow to dark brown exuviae positioned more or less centrally AONORL4.jpg . Beneath the scale cover, the adult female insect is pyriform initially, expanding with maturity to subcircular and becoming moderately sclerotized around margins. Scale cover of male similar in colour to the female but smaller, elongate oval, with subterminal yellow exuviae AOORL.jpg . The adult male is winged (Ghauri, 1962).
Body of slide-mounted adult female 1.0-1.4 mm long, becoming somewhat inflated and marginally sclerotized with maturity but never becoming reniform AOORO.jpg . (This is unusual for a member of the genus Aonidiella.) Prepygidial abdominal segments 1-3 each with a row or cluster of dorsal submarginal macroducts on either side AOORB.jpg . Pygidium with paraphyses present, most or all no longer than median lobes; perivulvar pores present in 4 (occasionally 5) groups; prevulvar apophyses and scleroses absent AOORP2.jpg ; plates lateral to third lobes each with a single fleshy process (not fringed) AOORMG.jpg .
Host range
A. orientalis is highly polyphagous: it has been recorded from hosts in 36 genera and 25 plant families (Davidson and Miller, 1990). It can attack almost any host except conifers (Williams and Watson, 1988). Oriental scale can be an economic pest of crops from diverse families, including species of Citrus and Ficus, mango, papaya, bananas and other fruits; tea (Camellia sinensis); and palm trees, including coconut and arecanut (Areca catechu). Host records include species of: Acacia, Aegle, Agave sisalana, Albizia, Annona spp., Areca catechu, Azadirachta, Bauhinia, Bombax, Calotropis, Camellia sinensis, Camellia spp., Carica papaya, Cassia, Citrus spp., Cocos nucifera, Codiaeum, Cucurbita, Cycas, Dalbergia, Diospyros, Elaeis guineensis, Eugenia spp., Feijoa, Ficus spp., Ficus carica, Gossypium hirsutum, Hedera, Hibiscus, Jasminum, Laelia, Litchi chinensis, Litsea, Mangifera indica, Manilkara, Melia, Metroxylon, Morus, Musa sapientum, Myrrhinium, Myrtaceae, Nerium, Olea europaea, Orchidaceae, Osbeckia, Palmae, Persea americana, Phoenix dactylifera, Pistacia, Podocarpus, Polyalthea, Poncirus, Prunus persica, Prunus spp., Psidium guajava, Punica granatum, Ricinus communis, Ricinus, Rosa, Roystonea, Salix, Santalum, Schleichera, Solanum melongena, Solanum spp., Spondias, Tamarindus, Vitis vinifera, Weinmannia, Ziziphus spp.
Affected plant stages: seedling, vegetative, flowering and fruiting stages.
Affected plant parts: leaves AONORL.jpg , stems AONORL3.jpg , and fruits/pods.
Biology and ecology
Aonidiella orientalis reproduces sexually; adult females probably produce species-specific sex pheromones to attract the winged adult males. Khalaf and Sokhansanj, 1993, found that reproduction was most frequently viviparous, but oviparous and ovoviviparous reproduction have been observed also (Farid, 1994). There are three generations per year in India (Glover, 1933). In Iran, five generations per year were recorded, with the maximum population density in the fourth and fifth generations. Four annual generations, two in winter and two in spring, were observed on weeping fig (Ficus benjamina) in Saudi Arabia (Badawi and Al-Ahmed, 1990).
In laboratory studies, males took an average of 19.5 days to proceed from the crawler stage to adult and females took an average of 44.2 days from the crawler stage to production of the first crawler of the subsequent generation (Elder and Smith, 1995). In Saudi Arabia, populations were lowest in summer, probably due to high temperatures (Badawi and Al-Ahmed, 1990).
The dispersal phase of A. orientalis is the first instar, or crawler, which has legs. Crawlers can walk up to perhaps 1 m, but can be distributed across much greater distances by wind, flying insects and birds and transport of infested plant material by man.
Symptoms
Direct feeding by A. orientalis on leaves and stems reduces plant vigour through the removal of plant sap. Feeding often causes discoloration and distortion of leaves AONORL.jpg and stems, probably due to the toxicity of saliva injected by the insects during feeding AONORL2.jpg . Heavy infestations can result in the yellowing of foliage and defoliation, dieback of small twigs and premature fruit drop (Rajagopal and Krishnamoorthy, 1996). Cosmetic damage may also occasionally occur to fruits.
Economic impact
A. orientalis is highly polyphagous and therefore potentially a serious pest of a wide range of crops. It is considered to be a serious pest in certain areas of the world, notably on coconut and arecanut in South India (Rajagopal and Krishnamoorthy, 1996), and on coconut in Florida, USA (Dekle, 1976). Damaging infestations of A. orientalis on neem in West Africa are associated with water stress (Boa, 1995). Schmutterer, 2001, records A. orientalis as the most important pest of neem (Azadirachta indica).It has been recorded as a pest on papaya fruit in Malaysia (Chua and Wood, 1990) and guava (Psidium guajava) in India (Hayes, 1970).
The greatest economic impact attributed to A. orientalis is often in areas it has recently invaded. In Australia, for example, A. orientalis first spread from the Torres Strait Islands to Queensland in 1956. It caused problems for the first time on papaya during 1988, and is now the most important pest on papaya in northern Queensland (Elder et al., 1998).
Aonidiella orientalis is an important pest of tamarind trees in India (Rajagopal and Krishnamoorthy, 1996), and of species of Citrus (especially Omani lime, sweet lime and grapefruit) in Iran (Farid, 1994) and Asia (Rosen, 1990a). It is also a serious pest on coconuts in Malaysia and Sri Lanka, mango in the Philippines and Israel, papaya in Malaysia and Australia, and guava in India (Rosen, 1990a). In Nigeria, Niger and northern Cameroon, A. orientalis infestations damage neem (Azadirachta indica) and can kill trees that are subject to extreme water stress (Boa, 1995).
In India and Indonesia, A. orientalis disrupts the production of lac (a resinous secretion from the scale insect Laccifer lacca) by feeding on the same hosts and thereby decreasing the quality and yield (Rajagopal and Krishnamoorthy, 1996).
Detection and inspection methods
Direct inspections can be made of leaves, aided by a x8 hand lens and a powerful torch if required, or by a dissection microscope in the laboratory. A. orientalis sometimes occurs also on branches, trunks, shoots and fruits of host plants. Look for circular, flat, pale-yellow to reddish-brown scales, 1.5-2.6 mm in diameter.
Phytosanitary risk
Aonidiella orientalis is of quarantine importance because it feeds on a wide variety of hosts and can be transported on infested plant material by man. The species was reported to be a relatively new introduction to the South Pacific region by Williams and Watson, 1988, and therefore to be of potential phytosanitary risk. In the Caribbean A. orientalis is regarded as an economic plant pest of quarantine importance (Schotman, 1989).
Natural enemies
Although A. orientalis has a wide distribution, its natural enemies have only been reported from a few countries, most notably India, Pakistan and Saudi Arabia (Rajagopal and Krishnamoorthy, 1996). A. orientalis on papaya in Queensland, Australia has been successfully controlled by the parasitoids Comperiella lemniscata and Encarsia citrina (Elder et al., 1998). C. lemniscata and two predatory coccinellids, Chilocorus circumdatus and C. baileyii, were introduced into Israel from Australia for the control of A. orientalis on mango (Ofek et al., 1997). Comperiella bifasciata and C. lemniscata are probably the only two parasitoids that are naturally effective at checking populations of A. orientalis over most of its range (Rajagopal and Krishnamoorthy, 1996). These authors also indicated the potential of the parasite Comperiella bifasciata and the predator Chilocorus nigrita as biological control agents. Coccinellid beetles and lacewings are frequent predators of A. orientalis on a variety of crops (Mani and Krishnamoorthy, 1996).
Observations in the species card on A. aurtantii, on the importance of the control of ants to maximise the effectiveness of natural enemies, are probably relevant to A. orientalis also.
Parasitoids:
- Aphytis lingnanensis, attacking: nymphs, in China, Taiwan and Japan. Introduced: USA (California), South Africa, Mexico, Argentina, Chile, Cyprus, Israel, Morocco
- Aphytis melinus, attacking: nymphs, in India, Pakistan. Introduced: USA (California), South Africa, Australia, Argentina, Chile, Cyprus, Israel, Italy, Morocco
- Comperiella bifasciata, attacking: nymphs, in India, China and Japan. Introduced: USA (California), South Africa, Swaziland, Australia, Mexico, Agrentina, Israel
- Comperiella lemniscata, attacking: nymphs, adults, in China and India. Introduced: Australia, Israel
- Encarsia citrina, attacking: nymphs, in Japan. Introduced to: USA; Australia; Mediterranean Basin; Turkey; Italy, Indonesia (Bali), Tahiti, Fiji, Cook Islands, Africa
- Habrolepis aspidioti, in Egypt
Predators:
- Chilocorus baileyi, attacking: nymphs, adults, in Australia, Israel (introduced)
- Chilocorus bipustulatus, attacking: nymphs, adults, in Israel, Iran
- Chilocorus circumdatus, attacking: nymphs, adults, in Australia, Israel (introduced)
- Chilocorus nigrita, attacking: eggs, nymphs, adults, in Oriental region, Indonesia. Introduced to: southern Africa, Oman, Seychelles, American Samoa, Hawaii, Pohnpei and Mauritius and has spread naturally.
Distribution
See Aonidiella orientalis distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species. Aonidiella orientalis is easily distinguished from most other Aonidiella species, as the prosoma of the adult female is less heavily sclerotized and fails to become strongly reniform at maturity AOINORS.jpg. It also has 3 conspicuous submarginal groups of macroducts on either side of the free abdominal segments. A key to separate five economically important species of Aonidiella in the tropics is given by Williams and Watson, 1988 (although this key does not include A. citrina). McKenzie, 1938, provided a key to separate the species of Aonidiella.
Aonidiella simplex (Grandpré and Charmoy) (A. andersoni (Laing) is a synonym) resembles A. orientalis in body shape, but lacks the perivulvar pores that are present in A. orientalis. Aonidiella simplex is known from Kenya, Tanzania, Mauritius and India (Karnataka) on species of Agave, Aloe, Asparagus, Cocos nucifora, Furcraea, Nerium, Ricinus, Solanum melongena and bamboo (The Natural History Museum collection, London, UK).
It is possible for inexperienced identifiers to confuse Aonidiella orientalis with some members of the genus Chrysomphalus (e.g. C. dictyospermi CHRDIP.jpg and C. pinnulifer CHRPINP1.jpg). However, members of Chrysomphalus lack sclerotization of the prosoma and have a paraphysis between the second and third lobes on either side, that is usually longer than a nearby lobe. In A. orientalis, the prosoma becomes sclerotized with maturity and the paraphysis between the second and third lobes on either side is shorter or the same length as a nearby lobe AOORP2.jpg. Williams and Watson, 1988, provide keys and illustrations.
Comments
Aonidiella orientalis is probably eastern Asian in origin. It is a tropical and subtropical species with a wide distribution, as it has been accidentally distributed worldwide by human transport of infested plants; it also occurs in greenhouses in temperate areas. There is no record from A. orientalis from Europe.
Asia
Afghanistan: present, no further details (Nakahara, 1982)
Bangladesh: no further details (Natural History Museum, London, UK)
Cambodia: present, no further details (Nakahara, 1982)
China
Guangdong: present, no further details (Tao, 1999)
Guangxi: present, no further details (Tao, 1999)
Hainan: present, no further details (Tao, 1999)
Hebei: present, no further details (Tao, 1999)
Hong Kong: present, no further details (Tao, 1999)
Sichuan: present, no further details (Tao, 1999)
Yunnan: present, no further details (Tao, 1999)
Dubai: The Natural History Museum collection, London, UK
India: present, no further details (CIE, 1978)
Andhra Pradesh: present, no further details (CIE, 1978)
Bihar: present, no further details (CIE, 1978)
Delhi: present, no further details (Natural History Museum, London, collected 1980)
Gujarat: present, no further details (Natural History Museum, London, UK)
Karnataka: present, no further details (Shafee and Fatma, 1984)
Kerala: present, no further details (Natural History Museum, London, UK)
Madhya Pradesh: present, no further details (CIE, 1978)
Maharashtra: present, no further details (CIE, 1978)
Nicobar Islands: present, no further details (CIE, 1978)
Orissa: present, no further details (Natural History Museum, London, UK)
Punjab: present, no further details (Natural History Museum, London, UK)
Tamil Nadu: present, no further details (CIE, 1978)
Uttar Pradesh: present, no further details (CIE, 1978)
West Bengal: present, no further details (Natural History Museum, London, UK)
Indonesia: present, no further details (Nakahara, 1982)
Iran: present, no further details (Seghatoleslami, 1977; Abivardi, 2001)
Iraq: present, no further details (CIE, 1978)
Israel: present, no further details (Wysoki, 1997)
Laos: present, no further details (Nakahara, 1982)
Malaysia
West Malaysia: present, no further details (CIE, 1978)
Maldive Is: present, no further details (Watson et al., 1995)
Myanmar: present, no further details (Nakahara, 1982)
Nepal: present, no further details (Nakahara, 1982)
Oman: present, no further details (Elwan, 2000)
Pakistan: present, no further details (Nakahara, 1982)
Philippines: present, no further details (Velasquez, 1971; Nakahara, 1982)
Saudi Arabia: present, no further details (Nakahara, 1982)
Singapore: present, no further details (Nakahara, 1982)
Sri Lanka: present, no further details (Nakahara, 1982)
Thailand: present, no further details (Nakahara, 1982)
Trucial States: The Natural History Museum collection, London, UK
United Arab Emirates: The Natural History Museum collection, London, UK
Vietnam: present, no further details (Nakahara, 1982)
Africa
Angola: The Natural History Museum collection, London, UK
Cameroon: The Natural History Museum collection, London, UK
Congo Democratic Republic: The Natural History Museum collection, London, UK
Egypt: The Natural History Museum collection, London, UK
Ethiopia: present, no further details (Nakahara, 1982)
Kenya: present, no further details (Nakahara, 1982)
Madagascar: present, no further details (Nakahara, 1982)
Mauritius: present, no further details (Nakahara, 1982)
Niger: The Natural History Museum collection, London, UK
Nigeria: The Natural History Museum collection, London, UK
North Africa: present, no further details (Beardsley, 1966)
Somalia: present, no further details (Nakahara, 1982)
South Africa: present, no further details (Nakahara, 1982)
St Helena: The Natural History Museum collection, London, UK
Sudan: present, no further details (Nakahara, 1982)
Tanzania: present, no further details (Nakahara, 1982)
Zambia: The Natural History Museum collection, London, UK
Western Hemisphere
Antigua: The Natural History Museum collection, London, UK
Bahamas: present, no further details (CIE, 1978; Miller, 1996)
Barbados: present, no further details (CIE, 1978)
Brazil: present, no further details (Nakahara, 1982; Kondo, 2001)
Guanabara: present, no further details (Silva et al., 1968)
Rio de Janeiro: present, no further details (Silva et al., 1968; Claps et al., 2001a)
Rio Grande do Sul: present, no further details (Silva et al., 1968; Claps et al., 2001a)
Santa Caterina: present, no further details (Silva et al., 1968; Claps et al., 2001a)
Colombia: present (Kondo, 2001)
Cuba: present, no further details (CIE, 1978)
Curaçao: present, no further details (CIE, 1978)
Dominican Republic: present, no further details (CIE, 1978)
Ecuador: The Natural History Museum collection, London, UK
Guadeloupe: present, no further details (CIE, 1978)
Haiti: present, no further details (CIE, 1978; Schotman, 1989)
Jamaica: present, no further details (CIE, 1978)
Martinique: present, no further details (CIE, 1978)
Mexico: present, no further details (CIE, 1978; Miller, 1996)
Netherlands Antilles: present, no further details (CIE, 1978)
Panama: present, no further details (CIE, 1978; Miller, 1996)
Puerto Rico: present, no further details (CIE, 1978)
St Kitts: The Natural History Museum collection, London, UK
Trinidad and Tobago: present, no further details (CIE, 1978)
USA
Florida: present, no further details (CIE, 1978; Miller, 1996)
United States Virgin Islands (St Thomas): The Natural History Museum collection, London, UK
Venezuela: present, no further details (Nakahara, 1982; Miller, 1996)
Oceania
Australia: present, no further details (Tao, 1999)
Northern Territory: present, no further details (CIE, 1978; CSIRO, 2001)
Queensland: present, no further details (CIE, 1978; CSIRO, 2001)
Nauru: The Natural History Museum collection, London, UK
Mariana Is: present, no further details (Nakahara, 1982)
Papua New Guinea: present (Williams and Watson, 1988)
South Mariana Is: present (Beardsley, 1966)
Yap Is: present, no further details (Nakahara, 1982; Beardsley, 1966)