(Morgan, 1889)
Diagnosis
Scale cover of adult female circular, flat, semitransparent, grey to light brown, with margin white or yellow; subcentral exuviae yellow or brown SELARTL1.jpg and SELARTL2.jpg . Scale cover of male elongate oval, smaller than that of female, lighter grey to light brown, with margin white or yellow; submarginal exuviae dark yellow (Davidson and Miller, 1990) SELARL.jpg .
Body of adult female about 0.85 mm long, strongly sclerotized, with a deep constriction between meso-and metathorax, dividing the semicircular prosoma from the tapering postsoma SELARS.jpg . Pygidium with median and second lobes subequal in size and similar in shape; third lobe reduced to a strongly sclerotized spine; perivulvar pores present in two groups SELARP.jpg .
Host range
Selenaspidus articulatus is a highly polyphagous species that has been recorded from hosts belonging to 60 genera in 31 plant families (Davidson and Miller, 1990). Hosts are often members of the families Anacardiaceae, Euphorbiaceae and Palmae. Species of Citrus are favoured hosts. Hosts include species of: Acalypha, Anacardium, Annona spp., Antidesma, Ardisia, Artocarpus heterophyllus, Arundinaria, Averrhoa spp., Barringtonia, Bauhinia, Bignonia, Brunfelsia, Calathea, Calea, Calophyllum, Camellia sinensis (tea), Carissa, Cassia, Celastrus, Ceratonia, Chrysalidocarpus, Chrysophyllum, Citrus spp., Claoxylon, Cocos nucifera, Codiaeum, Coffea spp., Cordyline, Croton, Cycas, Cyperaceae, Decaspermum, Dictyosperma, Dovyalis, Dracaena, Elaeis, Eriobotrya, Eucalyptus, Eugenia, Excoecaria, Ficus, Fortunella, Furcraea, Garcinia, Gardenia, Gliricidia, Hedera, Hedychium, Hevea brasiliensis, Hibiscus, Howea, Hyphaene, Ixora, Jacquemontia, Jasminum, Lagerstroemia, Lantana, Ligustrum, Litchi chinensis, Lonchocarpus, Maclura, Magnolia, Malachra, Mammea, Mangifera indica, Manihot, Mascarenhasia, Matayba, Mimusops, Musa, Neodypsis, Nephelium, Nerium, Olea europaea, Palmae, Pandanus, Passiflora edulis, Persea americana, Phaseolus, Phoenix dactylifera, Pilea, Plumeria, Rosa, Saccharum officinarum, Sambucus, Schinus, Spondias, Swietenia, Tamarindus, Tambourissa, Tecoma, Theobroma, Thespesia, Tricalysia, Vitis vinifera, Washingtonia and Xanthosoma sagittifolium.
Affected plant stages: vegetative growing, flowering, fruiting and post-harvest stages
Affected plant parts: on leaves (especially upper surfaces) SELARTL1.jpg , sometimes also on fruits/pods, growing points and stems; rarely on the bark.
Biology and ecology
Beingolea, 1969a, and Bartra, 1974, studied the biology of S. articulatus under laboratory conditions (summer, 26°C; winter, 17°C). Eggs are small (0.2 mm on their major axis), oval and flat. The species is ovoviviparous and emergence of the crawlers takes place immediately after the egg is laid. Crawlers preferentially settle at 20°C, in the light. Development of females typically follows the pattern: crawler; first; second and third sessile instars; immature adult (pigidium protected); mature female (pigidium retracted). In the male, the third instar is delayed, and the third moult (pupa) is recognizable by the oval shape of the scale cover and the scutiform shape of the body. Later in development they are recognizable by the eye spots of the prepupae, the shape of the scale cover and the pupal chamber. Prepupae, pupae and males are clearly visible through the thin scale cover. Individuals are frequently found in aggregations.
Selenaspidus articulatus occurs on both sides of the leaves, but mostly on the upper surface, exposed to the sun. The life cycle from egg to adult takes 30 days for the male and 45 days for the female. Reproduction starts at day 45 in females and peaks at day 80. Eggs are laid through a triangular, trap-like vulvar opening (Beingolea, 1969a). Typically each female produces 71-124 eggs on Citrus spp. High population densities are found most often at times of high rainfall and temperature (Perruso and Cassino, 1993). In Brazil (Sao Paulo), high temperature and humidity were found to favour dominance of S. articulatus over Parlatoria ziziphi on oranges (Watanabe et al., 2000b).
Mortality is often high in immature stages: 37.7% in crawlers under the mother scale; 46% of free-living crawlers in summer; 73% in winter (Bartra, 1974). Crawlers are the primary dispersal stage and move to new areas of the plant or are dispersed by wind or animal contact. Mortality due to abiotic factors is high in this stage. Dispersal of sessile adults and eggs occurs through human transport of infested plant material.
Symptoms
Selenaspidus articulatus multiplies rapidly on Citrus leaves and fruit, rapidly drying the tissues and sometimes killing the leaves and fruit (Williams and Watson, 1988). The damage is caused by sap-depletion, and through injection of toxic saliva, which causes chlorosis and death of plant tissue in the area of penetration.
Economic impact
Selenaspidus articulatus can be important pest on Citrus and coffee (especially Robusta coffee). On Citrus, S. articulatus rapidly dries the tissues and sometimes kills the tree (Swaine, 1971). It is the most important pest of olive and Citrus in Peru (Canales Canales and Valdivieso, 1999). Maddison, 1976, classed this species as a major pest of Citrus in Fiji, and Hinckley, 1965, recorded it killing Bauhinia, Lantana and Musa spp. there. In Brazil (Sao Paulo), Watanabe et al., 2000a, mention that the economic threshold level for S. articulatus on orange is 10 scales/leaf, and that the population levels in most orchards were above this level for most moths of the year. It is a problem on Citrus in Brazil (Sao Paulo) and is currently the subject of a biological control programme there (Claps et al., 2001a). The species is a pest of bananas in Central America and Jamaica (Chua and Wood, 1990). Selenaspidus articulatus was abundant on coffee in Mexico, and regarded as a potential pest of coffee by Ibarra Nunez, 1990.
Detection and inspection methods
Examine leaves, especially the upper surfaces, of the host-plants listed above, for circular, flat, semitransparent, grey to light brown scale covers, each with a white or yellow margin and yellow or brown subcentral exuviae SELARTL1.jpg .
Phytosanitary protection
Selenaspidus articulatus is mentioned on quarantine lists (Burger and Ulenberg, 1990).
Natural enemies
The introduction of Aphytis roseni to Peru in 1971 resulted in an increase in the rate of natural control of S. articulatus from 10% to 75% (Bartra, 1974), and occasionally up to 92% (Beingolea, 1994). Rhyzobius sp. causes ca 26% mortality of S. articulatus through predation in Peru (Beingolea, 1994).
Parasitoids:
- Aphytis aberrans, attacking: adults
- Aphytis chionaspis, attacking: adults
- Aphytis lingnanensis
- Aphytis roseni, attacking: nymphs, adults, in Kenya; Uganda; Introduced: Peru; Brazil
- Encarsia fasciata, attacking: nymphs, in the West Indies
- Encarsia lounsburyi, attacking: adults
- Habrolepis rouxi, attacking: nymphs, adults, in Kenya; Uganda
Predators:
- Azya luteipes
- Chilocorus cacti
- Chrysoperla sp., in Brazil (Rio de Janeiro)
- Coccidophilus citricola
- Hyperaspis
- Nephus
- Orius
- Pentilia egena, in Brazil (Rio de Janeiro)
- Pentilia insidiosa
- Rhyzobius lophanthae, attacking: nymphs, adults. Introduced: Peru
- Rhyzobius pulchellus, attacking: nymphs, adults, in Vanuatu, New Caledonia, Peru
- Signiphora spp., in Peru
Pathogens:
- Aschersonia aleyrodis
- Beauveria bassiana, in Peru
Distribution
See Selenaspidus articulatus distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Comments
Selenaspidus articulatus probably originated in Africa (Rosen, 1990b) or Madagascar. It is now a tropicopolitan species, the only member of this genus to have a wide distribution (Williams and Watson, 1988); it may be established under glass in a few localities in northern countries. The species has been eradicated in California (Gill, 1997). Literature records of S. articulatus in Chile were erroneous (Claps et al., 2001a). Selenaspidus articulatus has not been recorded from Australia, most of North America, or from many Pacific islands.
Europe: in greenhouses, no further details (Danzig and Pellizzari, 1998)
Asia
Philippines: present, no further details (Davidson and Miller, 1990; Miller, 1996)
Sri Lanka: present, no further details (CIE, 1981a)
Taiwan: present, no further details (Tao, 1999)
Turkey: present, no further details (Davidson and Miller, 1990)
Africa
Angola: present, no further details (Nakahara, 1982)
Benin: present, no further details (Nakahara, 1982)
Cameroon: present, no further details (Nakahara, 1982)
Chad: present, no further details (Nakahara, 1982)
Congo Democratic Republic: present, no further details (Nakahara, 1982)
Côte d'Ivoire: present, no further details (Nakahara, 1982)
Eritrea: The Natural History Museum collection, London, UK
Ethiopia: present, no further details (Nakahara, 1982)
Ghana: present, no further details (Nakahara, 1982)
Guinea: present, no further details (Nakahara, 1982)
Kenya: present, no further details (Greathead, 1976a)
Madagascar: present, no further details (Nakahara, 1982)
Mali: present, no further details (CIE, 1981a)
Mauritius: present, no further details (Williams and Williams, 1988)
Morocco: present, no further details (Nakahara, 1982)
Mozambique: present, no further details (Nakahara, 1982)
Niger: present, no further details (CIE, 1981a)
Nigeria: present, no further details (CIE, 1981a)
Principe: present, no further details (Nakahara, 1982)
Réunion: present, no further details (Williams and Williams, 1988)
Sao Tomé: present, no further details (Nakahara, 1982)
Sierra Leone: present, no further details (Nakahara, 1982)
Somalia: present, no further details (Nakahara, 1982)
South Africa: present, no further details (Nakahara, 1982)
Sudan: present, no further details (CIE, 1981a)
Tanzania: present, no further details (Nakahara, 1982)
Togo: present, no further details (Nakahara, 1982)
Uganda: present, no further details (Beingolea, 1994; Prinsloo and Neser, 1994)
Zambia: present, no further details (CIE, 1981a)
Zimbabwe: present, no further details (Nakahara, 1982)
Western Hemisphere
Antigua: present, no further details (CIE, 1981a)
Bahamas: The Natural History Museum collection, London, UK
Barbados: present, no further details (Bennett and Alam, 1985)
Belize: The Natural History Museum collection, London, UK
Bermuda: present (Nakahara, 1982; Hodgson and Hilburn, 1991)
Bolivia: present, no further details (Squire, 1972a; CAN, 1994)
Brazil
Pará: present, no further details (Claps et al., 2001a)
Paraná: present, no further details (Silva et al., 1968)
Rio de Janeiro: present, no further details (Perruso and Cassino, 1997)
Sao Paulo: present, no further details (Santos and Gravena, 1995; Watanabe et al., 2000a; Claps et al., 2001a)
Colombia: present, no further details (Agudelo and Falcon, 1977; Kondo, 2001)
Costa Rica: present, no further details (CIE, 1981a)
Cuba: present, no further details (Suris et al., 1989)
Dominica: present, no further details (CIE, 1981a)
Dominican Republic: present, no further details (CIE, 1981a)
Ecuador: present, no further details (CIE, 1981a; CAN, 1994; Kondo, 2001)
El Salvador: present, no further details (CIE, 1981a)
Grenada: present, no further details (CIE, 1981a)
Guadeloupe: present, no further details (CIE, 1981a)
Guatemala: present, no further details (CIE, 1981a)
Guyana: present, no further details (Danzig and Pellizzari, 1998)
Haiti: present, no further details (CIE, 1981a)
Honduras: present, no further details (CIE, 1981a)
Jamaica: present, no further details (CIE, 1981a)
Martinique: present, no further details (CIE, 1981a)
Mexico: present, no further details (Ibarra Nunez, 1990; Miller, 1996)
Montserrat: present, no further details (CIE, 1981a)
Nicaragua: present, no further details (CIE, 1981a)
Panama: present, no further details (CIE, 1981a)
Peru: widespread (Beingolea, 1969a; Beingolea, 1969b; Beingolea, 1994; Bartra, 1974)
Puerto Rico: present, no further details (CIE, 1981a)
St Lucia: present, no further details (CIE, 1981a)
St Vincent: present, no further details (CIE, 1981a)
Suriname: present, no further details (CIE, 1981a)
Trinidad and Tobago: present, no further details (CIE, 1981a)
USA
Florida: present, no further details (Nakahara, 1982)
United States Virgin Is: present, no further details (CIE, 1981a)
Venezuela: present, no further details (Clavijo, 1977; CAN, 1994)
Oceania
Fiji: present (Williams and Watson, 1988)
Guam: present, no further details (Nakahara, 1982)
Solomon Is: present (Williams and Watson, 1988)