(Packard, 1869)
Diagnosis
In life, scale cover of adult female 2.5-3.5 mm long, elongate and parallel-sided, slightly convex, not strongly tapered towards the exuvial end; brownish-yellow (young) to dark brown (old), with yellowish-brown exuviae at the narrow end LEGLL2.jpg and LEGLOL3.jpg . Together with the dorsal cover, a membranous ventral scale cover is secreted which separates the insect from the host plant surface (Bruwer, 1998). Second instar exuviae of the female with a distinctive reddish-brown spot at the posterior end, like L. beckii. Male scale cover similar to that of female but smaller, with yellow terminal exuviae LEGLOL.jpg . Body of adult female white (Gill, 1997).
Body of slide-mounted adult female elongate, more than 1.8x as long as wide; thorax becoming sclerotized at maturity; head without obvious lateral tubercles; eye not developed into a spur; sclerotized, pointed marginal spurs present on abdominal segments II, III and IV; sclerotized dorsal bosses absent LEGLOS.jpg . Pygidium with median lobes with a pair of gland spines between them, not yoked, and without club-shaped basal scleroses; perivulvar pores present; and with six marginal macroducts on each side LEGLOP.jpg .
Host range
Lepidosaphes gloverii is a polyphagous species. According to Davidson and Miller, 1990, its host range covers eight plant families and 19 genera, but it may well be wider. Citrus and related species are favoured hosts. Danzig and Pellizzari, 1998, reported that it is found only on Citrus in Mediterranean countries and the former USSR. Hosts include species of: Alocasia, Buxus, Carissa, Citrus spp., Cocos nucifera, Codiaeum variegatum, Damnacanthus, Erythrina spp., Eugenia, Euonymus japonicus, Fortunella, Magnolia, Mangifera indica, Palmae, Poncirus, Populus, Salix and Sciadopitys.
Affected plant stages: vegetative growing, flowering, fruiting and post-harvest stages
Affected plant parts: aerial parts, mainly on bark, leaves LEGLL3.jpg and fruit
Biology and ecology
Bruwer, 1998, summarized the life history of L. gloverii: reproduction is sexual, and each female lays about 200 eggs, arranged in two rows between the dorsal and ventral scale covers. The eggs changed colour from white to purple just before hatching. The mobile crawlers (first instars) settled on twigs, leaves and fruit within 12 hours of hatching. At a constant 30°C and 75% RH, eggs hatched after about 14 days. The first moult was completed 11 days after the crawler settled. The second instar took a further 8-9 days, the second moult started after 5 days. The winged male finally emerged from the pupa approximately 42 days after the crawlers settled. The adult female was fertilized about 7 days after her second moult, and the first eggs were laid 6 days later.
In mass-rearing experiments on lemons, also at 30°C and 75 ± 5% RH, the shortest mean duration of the immature stages was 32 days; the shortest mean generation time (crawler to crawler) was 67 days; the highest intrinsic rate of natural increase (r) was 0.396 and the highest reproductive potential was 44 crawlers per female. Other advantages of this combination of host, temperature and RH were the high percentage of crawler-producing females (63.3%) and the high percentage of crawler settlement (95.7%) (Bruwer, 1998).
According to Murakami, 1970, L. gloverii has two generations per year in Japan. In South Africa, although all stages of L. gloverii are present throughout the year without any dormant stage, life tables calculated by Bruwer, 1998, show a succession of four distinct peaks of each stage, representing four field generations annually. In California there are 3-4 generations per year (Gill, 1997).
Lepidosaphes gloverii has microclimatic preferences that result in it mainly infesting the interior part of the canopy (Bruwer, 1998). In California, it seems unable to survive hot, dry summers (Gill, 1997).
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
A heavy infestation of L. gloverii can delay the development of yellow colour in maturing Citrus fruit because the area around the scale insect remains green (Bruwer, 1998). Spotting of the fruit can reduce their market value or make them unmarketable. Another direct result of a heavy infestation is complete yellowing of the leaves, followed by leaf drop and twig dieback (Bruwer, 1998); this debilitates the tree and reduces productivity.
Economic impact
Due to the introduction of parasitoids to many countries to control L. gloverii populations, this species is now of less importance than it was. However, it is still occasionally sufficiently serious a pest to require control, e.g. on mango in India (Chua and Wood, 1990). Lepidosaphes gloverii was recorded as a major pest of Citrus in Fiji by Maddison, 1976. It occasionally causes problems at high altitudes in Argentina (Claps et al., 2001a). Danzig and Pellizzari, 1998, described it as a pest in the Palaearctic region, and Foldi, 2001, listed it as an occasional pest in France. In California it is a minor pest of Citrus (Gill, 1997).
Detection and inspection methods
In good light, inspect the bark, leaves and fruit for light to dark brown, elongate scale covers, not strongly tapered towards the exuvial end LEGLL2.jpg and LEGLOL3.jpg . Pay particular attention to the inner canopy, away from direct sunlight.
Phytosanitary risk
Species of armoured scale insects for which certain countries have established official quarantine measures are enumerated in quarantine lists. However, not all countries mention quarantine species, but formulate their quarantine measures in such a manner that the risk of introducing harmful alien species is minimized. Lepidosaphes gloverii is on the quarantine lists of certain countries (Burger and Ulenberg, 1990).
Natural enemies
The key to success for the biological control of L. beckii and other scale insects on Citrus is the control of ants. Ants, such as the pugnacious (Anoplolepis custodiens) and brown house (Pheidole megacephala) ants, are important indirect pests that can easily upset the natural balance between pest and natural enemy (Bruwer, 1998).
Parasitoids:
- Aphytis, attacking: nymphs, in Argentina, Mexico (introduced)
- Aphytis chrysomphali, attacking: nymphs in Australia
- Aphytis immaculatus, attacking: nymphs, in Taiwan
- Aphytis lepidosaphes, attacking: nymphs, adults, in Australia, South Africa
- Aphytis lingnanensis, attacking: nymphs, in China, Taiwan and Japan. Introduced to USA (California), South Africa, Australia, Mexico, Argentina, Chile, Cyprus, Israel, Morocco, Spain
- Encarsia citrina, attacking: nymphs, adults, in USA, South Africa
- Encarsia elongata, attacking: nymphs, in China, USA (introduced), Spain (introduced)
- Encarsia herndoni, attacking: nymphs, adults
- Encarsia lounsburyi, attacking: nymphs, in USA (introduced)
Predators:
- Aleurodothrips fasciapennis, attacking: eggs, nymphs, adults, in Indonesia; introduced to: Fiji
- Chilocorus nigrita, attacking: nymphs, adults, in South Africa (introduced)
- Chilocorus distigma
- Haplothrips merrilli, in Cuba, USA (Florida), Puerto Rico
- Hemisarcoptes coccophagus
- Pharoscymnus tomeensis
- Prosocheyla hepburni
- Rhyzobius lophanthae
Distribution
See Lepidosaphes gloverii distribution.
In life, L. gloverii can be distinguished from L. beckii by having a longer, narrower scale cover. These species often occur together on citrus.
Lepidosaphes gloverii can be distinguished from species of Unaspis in life by the colour of the male scale covers, which are brown in L. gloverii and white and carinated in Unaspis species (Gill, 1997). Female scale covers of Unaspis have a median longitudinal ridge that is absent from the covers of Lepidosaphes species.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species. Lepidosaphes gloverii differs from most other mussel scales in having sclerotized cuticle on the thorax in mature specimens.
Comments
Lepidosaphes gloverii is probably a native of the Far East (Gill, 1997) but now is widely distributed throughout the tropical and subtropical regions of the world (Nakahara, 1982), wherever Citrus is grown. In northern countries this species occurs only under glass (Danzig and Pellizzari, 1998). In spite of the record published by Danzig and Pellizzari, 1998, L. gloverii is not established in the United Kingdom (C.P. Malumphy, Central Science Laboratory, UK, pers. comm.).
Europe
Former USSR
Azerbaijan: present, no further details (CIE, 1962a)
Belarus: present, no further details (CIE, 1962a)
Caucasus: present, no further details (CIE, 1962a)
Georgia, Repubic of: present, no further details (CIE, 1962a)
Russian Federation: present, no further details (CIE, 1962a; Rose, 1990)
Transcaucasus: present, no further details (Danzig and Pellizzari, 1998)
France: present, no further details (Bénassy and Brun, 1999; Foldi, 2001)
Corsica: present, no further details (CIE, 1962a)
Greece: present, no further details (CIE, 1962a)
Italy: present in the south (Longo et al., 1995)
Sardinia: present, no further details (Longo et al., 1995)
Sicily: present, no further details (Longo et al., 1995)
Spain: present in Alicante, Cádiz, Castellón, Grenada, Murcia and Valencia (Amparo Blay Golcoechea, 1993)
Balearic Is: present, no further details (Amparo Blay Golcoechea, 1993)
Asia
Bhutan: The Natural History Museum collection, London, UK
China: present, no further details (Danzig and Pellizzari, 1998)
Fujian: present, no further details (CIE, 1962a)
Guangdong: present, no further details (CIE, 1962a)
Hainan: present, no further details (Tao, 1999)
Hubei: present, no further details (CIE, 1962a)
Hong Kong: present, no further details (CIE, 1962a)
Jiangsu: present, no further details (CIE, 1962a)
Shaanxi: present, no further details (Tao, 1999)
Shandong: present, no further details (Tao, 1999)
Shanxi: present, no further details (Xie, 1982)
India
Bihar: present, no further details (CIE, 1962a)
Karnataka: The Natural History Museum collection, London, UK
Indonesia: present, no further details (CIE, 1962a)
Bali: The Natural History Museum collection, London, UK
Iran: present, no further details (Seghatoleslami, 1977; Abivardi, 2001)
Israel: present, no further details (CIE, 1962a)
Japan: present (Kawai, 1980; Rose, 1990)
Honshu: present, no further details (CIE, 1962a)
Kyushu: present, no further details (CIE, 1962a)
Shikoku: present, no further details (CIE, 1962a)
Korea, DPR: present, no further details (CIE, 1962a)
Korea, Republic of: present, no further details (CIE, 1962a)
Lebanon: present, no further details (CIE, 1962a)
Malaysia
West Malaysia: present, no further details (CIE, 1962a)
Myanmar: present, no further details (CIE, 1962a)
Pakistan: present, no further details (CIE, 1962a)
Philippines: present, no further details (CIE, 1962a)
Ryukyu Archipelago: present, no further details (CIE, 1962a)
Sri Lanka: present, no further details (CIE, 1962a)
Thailand: present, no further details (CIE, 1962a)
Taiwan: present, no further details (Takagi, 1970; Wong et al., 1999)
Turkey: present, no further details (CIE, 1962; Danzig and Pellizzari, 1998)
Africa
Algeria: present, no further details (CIE, 1962a; Danzig and Pellizzari, 1998)
Cameroon: present, no further details (CIE, 1962a)
Egypt: present, no further details (CIE, 1962a; Danzig and Pellizzari, 1998)
Gambia: present, no further details (CIE, 1962a)
Ghana: The Natural History Museum collection, London, UK
Guinea: present, no further details (CIE, 1962a)
Madagascar: present, no further details (CIE, 1962a)
Mauritius: present, no further details (CIE, 1962a; Williams and Williams, 1988)
Morocco: present, no further details (CIE, 1962a; Danzig and Pellizzari, 1998)
Mozambique: present, no further details (CIE, 1962a)
Nigeria: present, no further details (CIE, 1962a; Eguagie, 1972)
Réunion: present, no further details (CIE, 1962a; Williams and Williams, 1988)
Sao Tomé: present, no further details (CIE, 1962a)
Senegal: present, no further details (CIE, 1962a)
Sierra Leone: present, no further details (CIE, 1962a)
South Africa: widespread (Bruwer, 1998)
Tanzania: present, no further details (CIE, 1962a)
Zimbabwe: The Natural History Museum collection, London, UK
Uganda: present, no further details (CIE, 1962a)
Western Hemisphere
Argentina: common in the North-East (Claps and Terán, 2001; Claps et al., 2001a)
Buenos Aires: present, no further details (Claps et al., 2001a)
Jujuy: present, no further details (Claps et al., 2001a)
Entre Rios: present, no further details (Claps et al., 2001a)
Salta: present, no further details (Claps et al., 2001a)
Tucumán: present, no further details (Claps et al., 2001a)
Belize: The Natural History Museum collection, London, UK
Bolivia: present, no further details (CIE, 1962; Squire, 1972a)
Brazil
Bahia: present, no further details (Claps et al., 2001a)
Espírito Santo: present, no further details (Claps et al., 2001a)
Minas Gerais: present, no further details (Claps et al., 2001a)
Pará: present, no further details (Claps et al., 2001a)
Pernambuco: present, no further details (Claps et al., 2001a)
Rio de Janeiro: present, no further details (Claps et al., 2001a)
Rio Grande do Sul: occurs in heavy infestations on Citrus (Claps et al., 2001a)
Santa Caterina: present, no further details (Claps et al., 2001a)
Sao Paulo: present, no further details (Claps et al., 2001a)
Cayman Is: The Natural History Museum collection, London, UK
Chile
Tarapacá: occasionally reported (Claps et al., 2001a)
Colombia: present (Kondo, 2001)
Costa Rica: present, no further details (CIE, 1962a)
Cuba: present, no further details (CIE, 1962a; Rose, 1990)
Curaçao: The Natural History Museum collection, London, UK
Dominican Republic: present, no further details (CIE, 1962a)
Ecuador: present, no further details (CIE, 1962a; Rose, 1990)
Guatemala: The Natural History Museum collection, London, UK
Honduras: present, no further details (CIE, 1962a)
Jamaica: present, no further details (CIE, 1962a)
Mexico: present (Rose, 1990; Miller, 1996)
Puerto Rico: present, no further details (Rose, 1990)
Suriname: present, no further details (CIE, 1962a)
Trinidad: present, no further details (CIE, 1962a; Rose, 1990)
USA
Alabama: present, no further details (CIE, 1962a; Nakahara, 1982)
California: restricted distribution, uncommon (Gill, 1997)
Florida: present, no further details (Nakahara, 1982; Danzig and Pellizzari, 1998)
Hawaii: present on Oahu (Heu, 2002)
Louisiana: present, no further details (CIE, 1962a; Nakahara, 1982)
Oklahoma: under glass (Nakahara, 1982)
South Carolina: present, no further details (Nakahara, 1982)
Texas: present, no further details (Rose, 1990; Woolley, 1994)
Venezuela: present, no further details (CIE, 1962a)
Oceania
Australia: present, no further details (CIE, 1962a)
New South Wales: present, no further details (CIE, 1962a; CSIRO, 2001)
Northern Territory: The Natural History Museum collection, London, UK
Queensland: present, no further details (CSIRO, 2001)
Bonin Is: present (Beardsley, 1966)
Caroline Is: present, no further details (CIE, 1962a)
Cook Is: present (Williams and Watson, 1988)
Fiji: present (Williams and Watson, 1988)
French Polynesia: present, no further details (CIE, 1962a)
Niue: present (Williams and Watson, 1988)
Northern Mariana Is: present, no further details (CIE, 1962a)
Papua New Guinea: present (Williams and Watson, 1988)
Pohnpei: present (Beardsley, 1966)
Samoa: present, no further details (Williams and Watson, 1988)
Society Is: present (Williams and Watson, 1988)
South Mariana Is: present (Beardsley, 1966)
Tonga: present (Williams and Watson, 1988)
Truk Is: present (Beardsley, 1966)
Western Samoa: present (Williams and Watson, 1988)