Leonardi, 1906
Diagnosis
Scale cover of adult female in life 1.8-2.0 mm across, translucent pale buff but with adult body colour showing through; with translucent subcentral exuviae AONTAXL1.jpg . Scale cover of male elongate oval, about 1.4 mm long, with translucent subcentral exuviae AOTAXL.jpg . Body of adult female quickly becomes reniform; light brown initially, becoming brownish red with age (as the body fills with eggs) AONTAXL1.jpg .Adult male winged ([l][m]Literature[/m][r]Stoetzel, 1975[/r]Stoetzel, 1975).
Body of slide-mounted adult female 0.7-1.2 mm across; prosoma becoming highly sclerotized and expanded with maturity; eventually the lateral lobes may project further posteriorly than the apex of the pygidium AOTAXS.jpg . (This reniform shape characterises the genera Aonidiella and Africonidia (Ben-Dov, 1990a), although Aspidiotus macfarlanei is also reniform (Williams and Watson, 1988)). A sclerotized spur is sometimes present on either side of prosoma, level with mouthparts; abdominal segments without any prepygidial macroducts. Pygidium with paraphyses present, most or all no longer than median lobes; perivulvar pores absent; prevulvar apophyses and scleroses both absent AOTAXP2.jpg ; plates lateral to third lobes each fringed (not with a single fleshy process) AOTAXMG.jpg .
Host range
Aonidiella taxus has been recorded on twigs and leaves of evergreen species belonging to the genera Cephalotaxus, Podocarpus and Taxus (Borchsenius, 1966; Zahradník, 1990).
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: on undersides of needles/leaves AONTAXL1.jpg and occasionally on twigs
Biology and ecology
Reproduction is sexual and viviparous, and there are two or three generations per year in Japan (Uematsu, 1978); all developmental stages occur on the host in winter. In China (Shanghai), A. taxus has 3 or 4 generations per year, and fertilized adult females and second-instar nymphs overwinter on leaves (Qin et al., 1997). In Japan, the time from settling of the crawlers to the deposition of nymphs was more than 43 days for adult females kept at 25 deg C. Adult males emerged about 26 days after settling as crawlers. The developmental thresholds were 14.7 deg C for males and 14.8 deg C for females, and the temperature sums were 447 day-degrees C for females (from settling to nymph deposition) and 278 day-degrees C for males (from settling to adult emergence). Adult females deposited 2-6 crawlers/day and continued deposition for about 70 days. Fecundity averaged 158/female, the net reproduction rate was 59, the mean length of a generation 66 days, and the intrinsic rate of natural increase was 0.04/female daily at 25° C (Uematsu, 1978).
If the temperature is 0°C, about 98% of the first instar larvae die, and -2°C kills old females also; only second instar and young (fertilized) adult females overwinter (Zahradník, 1990). Stoetzel, 1975, found continuous reproduction with overlapping generations on Podocarpus under glass in USA (Virginia), with each adult female laying 3-5 eggs per day throughout their lives.
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
Toxic saliva injected into the host tissues during feeding cause chlorosis of the leaf around the stylet path AONTAXL2.jpg .
Economic impact
Aonidiella taxus damages ornamental conifers in parks and gardens (Zahradník, 1990).
Detection and inspection methods
Direct inspections can be made of the leaves and twigs, aided by a x8 hand lens and a powerful torch if required, or by a dissection microscope in the laboratory.
Natural enemies
Parasitoids:
- Aphytis sp., in Japan
- Aphytis yasumatsui, in Japan
- Comperiella bifasciata, in Japan
- Encarsia citrina, in Italy, Japan
- Encarsia spp., in Japan
Distribution
See Aonidiella taxus distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Aonidiella taxus AOTAXP2.jpg could be confused with A. aurantii, A. citrina and A. inornata McKenzie, as all four species lack perivulvar pores. A. taxus does not normally infest bark, unlike A. aurantii. A. taxus and A. inornata AOINORP.jpg lack prevulvar scleroses and apophyses, whereas A. aurantii AOAUP.jpg possesses both prevulvar apophyses and scleroses and A. citrina AOCIP.jpg possesses prevulvar apophyses. A. taxus has all the pygidial lobes of about the same size, whereas in A. inornata they are graduated in size, with the median lobes largest. The precise identity of A. inornata requires research, as its morphology is rather variable; Williams and Watson, 1988 remark that it may be a synonym of A. comperei or A. eremocitri (which typically possess perivulvar pores). 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.
According to the literature, A. inornata AOINORP.jpg is fairly polyphagous on the leaves and fruit of hosts including species of Allamanda, Annesijoa, Areca, Artocarpus, Astronia, Barringtonia, Bischofia, Campnosperma, Carica, Citrus, Cocos, Cordyline, Cycas, Dracaena, Elettaria, Euphorbia, Hedyotis, Jasminum, Mangifera, Melaleuca, Metroxylon, Musa, Nerium, Pandanus, Piper, Plumeria and Vitis vinifera. It is known from India (Uttar Pradesh), Maldives, Indonesia (including Irian Jaya), Laos, West Malaysia, Sarawak, Brunei Darussalam, Thailand, China (Hainan, Hebei, Hong Kong, Inner Mongolia, Liaoning, Yunnan), South-East Asia, Taiwan, Japan, Okinawa, Philippines, Papua New Guinea, Australia (Queensland), Guam, Caroline Is, Marshall Is, Palau, Is, Pohnpei, Truk, Wake Is, Yap Is, Kiribati, Vanuatu, Fiji, Western Samoa, USA (Hawaii), Cayman Is, Puerto Rico and East Africa (Pemba I., Tanzania) (Takagi, 1969; Velasquez, 1971; Kawai, 1980; Nakahara, 1982; Williams and Watson, 1988; Watson et al., 1995; Danzig and Pellizzari, 1998; Tao, 1999; Heu, 2002; The Natural History Museum collection, London, UK). AOINORS.jpg
It is possible for inexperienced identifiers to confuse Aspidiotus macfarlanei Williams and Watson with Aonidiella taxus. Aspidiotus macfarlanei also develops a sclerotized, reniform body at maturity ASPMACS.jpg (Williams and Watson, 1988), but has marginal prepygidial macroducts and lacks paraphyses on the pygidium ASPMACP.jpg. Aonidiella taxus lacks marginal prepygidial macroducts, and possesses paraphyses AOTAXP2.jpg. Aspidiotus macfarlanei has been recorded from the Solomon Islands on Carica papaya and Cocos nucifera.
Comments
Balachowsky, 1948, remarked that Aonidiella taxus was not of Palaearctic origin; it probably originated in the Oriental region. It has not been recorded from Australia, or from the Pacific islands.
Europe
Former USSR
Crimea: present, no further details (Nakahara, 1982)
Georgia, Republic of: Black Sea coast (Nakahara, 1982; Zahradník, 1990)
South European Territory: present, no further details (Danzig and Pellizzari, 1998)
France: present, no further details (Foldi, 2001)
Italy: present, no further details (Longo et al., 1995)
Sicily: present, no further details (Longo et al., 1995)
?Spain: only mentioned by Lupo, 1954; no material seen by Amparo Blay Golcoechea, 1993
Asia
China: present, no further details (Danzig and Pellizzari, 1998)
Japan: present (Kawai, 1980; Zahradník, 1990; Tao, 1999)
Korea: present, no further details (Tao, 1999)
Philippines: present, no further details (Velasquez, 1971)
Africa
Algeria: present, no further details (Danzig and Pellizzari, 1998)
Western Hemisphere
Argentina: present, no further details (Nakahara, 1982)
Buenos Aires: present, no further details (Claps et al., 2001a)
Brazil: present, no further details (Borchsenius, 1966; Nakahara, 1982) but there have not been any recent record (Claps et al., 2001a)
North America: present, no further details (Zahradník, 1990; Danzig and Pellizzari, 1998)
USA
Alabama: present, no further details (Nakahara, 1982)
Florida: present, no further details (Nakahara, 1982)
Louisiana: present, no further details (Nakahara, 1982)
Maryland: present, no further details (Nakahara, 1982)