(Lucas, 1853)
Diagnosis
Scale cover of adult female 1.25-1.4 mm long and 0.6-0.75 mm wide; consisting of black second-instar exuviae, subrectanglar with rounded corners, with a lip of white wax on the posterior margin PARLZIL.jpg and PAZIL2.jpg . The first-instar exuviae is attached to the anterior margin of the second-instar exuviae. Scale cover of male is white, 0.8 mm long, flat, with rather large, brown or black, terminal exuviae PAZIL.jpg and PARLZIL.jpg .
Body of slide-mounted adult female membranous, elongate oval with an ear-like lateral lobe on each side of the head, level with the anterior spiracles; two-bar ducts present; fringed plates extending as far forward as abdominal segment 2; submarginal duct tubercles present in a group on each side of the mesothorax; eyespot small, rounded and inconspicuous; and membranous derm pockets absent PAZIS.jpg . Pygidium with three pairs of rounded unilibulate lobes, fourth lobes present as sclerotized points, fifth lobes plate-like; 3 plates present between lobes 3 and 4 on each side; and without any submedian macroducts within the frame formed by the perivulvar pores PAZIP.jpg .
McKenzie, 1945, gives a detailed morphological description, illustrations and a key to the many species of Parlatoria.
Host range
Parlatoria ziziphi has been recorded from hosts belonging to five plant families (Borchsenius, 1966) but is usually found on Citrus and other Rutaceae (Williams and Williams, 1988). Records on other plants, such as palms including Phoenix dactylifera, and Psidium sp., may be unreliable (Dekle, 1976). Attempts to rear Parlatoria ziziphi on potato tubers and pumpkins failed (Li and Liao, 1990). Hosts include species of: Citrus spp., Codiaeum, Cymbidium, Damnacanthus, Ligustrum, Murraya paniculata, Poncirus, Severinia buxifolia and Ziziphus.
Affected plant stages: vegetative growing, flowering, fruiting and post-harvest stages
Affected plant parts: all aerial parts of the plant, especially the upper surfaces of leaves PARLZIL.jpg
Biology and ecology
The following paragraph is based on studies in Egypt by Sweilem et al., 1984; El Bolok et al., 1984a and El Bolok et al., 1984b, on sour oranges in under field and laboratory conditions; and by Salama et al., 1985a, and Salama et al., 1985b, on grapefruit. Parlatoria ziziphi reproduced sexually and had two generations per year on sour oranges, and three generations per year on grapefruit. Each female produced about 34 eggs on average, and the females feeding on fruit laid more eggs than those feeding on the branches or foliage. The shortest incubation period under controlled conditions was 4.4 days (27°C and 65% relative humidity). At natural temperatures (8.4-34.6°C), the incubation period varied from 5.4 to 12.1 days; the nymphal stage took 23.5 - 34.8 days for females and 28.6 - 49.4 days for males; and adult longevity was 50.8 - 88.2 days for females and 1.4 - 3.4 days for males. The most favourable time for population increase in 1982 was April (mean temperature 23.3°C and 58.6% relative humidity) and in 1983 it was September (mean temperature 26.4°C and 61.6% relative humidity). Population density was positively influenced by temperature and negatively influenced by relative humidity and (to a lesser extent) by rainfall. Nymphs formed 39% of the population. The highest population densities were usually in the lowest part of the canopy, facing west and south. Most scales settled on the upper leaf surface; the lower surface only became infested at very high population densities. Excess amounts of nitrogen or phosphorus given to sweet and baldi orange seedlings caused an increase in the population density of P. ziziphi. Added calcium had no effect, but potassium and magnesium had some effect, which varied according to the Citrus variety.
In China, P. ziziphi had three to four overlapping generations each year and overwintered in the adult stage (Huang et al., 1988). The oviposition period lasted for 79-135 days and the eggs took a mean of 7.8-11.6 days to hatch; 89.7-99.7% of the eggs hatched.
In Brazil (Sao Paulo), Watanabe et al., 2000a, mention that P. ziziphi on Citrus is less adversely affected by low temperature and humidity than its competitor, Selenaspidus articulatus.
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
Symptoms include black, subrectangular scales present on shoots, foliage and fruit, but especially on upper leaf surfaces. Depletion of plant sap leads to reduced host vigour, and the foliage and fruit may be discoloured with yellow streaking and spotting due to saliva toxicity. Heavy infestations may result in premature shedding of the leaves and fruit.
Economic impact
Parlatoria ziziphi is known as a pest of Citrus but there are few details available on the economic losses caused by this insect. Heavy infestations of Citrus cause premature senescence and leaf drop, reducing productivity. The species has become the most important pest of Citrus in Egypt (Coll and Abd-Rabou, 1998). Danzig and Pellizzari, 1998, describe it as a pest, and Foldi, 2001, lists it as an economically important pest in France. Parlatoria ziziphi was reported causing serious damage in East Java on varieties of Citrus nobilis, where shoots and leaves were attacked (Kalshoven and Laan, 1981).
Phytosanitary risk
In the UK and USA, P. ziziphi is often intercepted on imported Citrus produce. Immature and adult female P. ziziphi are readily carried on plants and plant produce and may be injurious when introduced to new geographical areas without natural enemies. Injudicious spraying of chemical pesticides can reduce natural enemy populations, allowing P. ziziphi to proliferate.
Detection and inspection methods
Examine aerial parts of the host-plants listed above, especially the leaves, for black, subrectanglar scale covers, each with rounded corners and some with a lip of white wax on the posterior margin PARLZIL.jpg . The small size, dark colour and sessile nature of the scales makes them difficult to detect unless present in large numbers. They are conspicuous on pale foliage or fruits such as oranges and lemons, because of the contrast in colour, but are easily confused with dirt particles when present on a dark background. All fresh Citrus material, especially leaves, should be thoroughly inspected.
Phytosanitary protection
Parlatoria zizphi is mentioned on quarantine lists (Burger and Ulenberg, 1990).
Natural enemies
See Rosen, 1990a, for a discussion of the natural enemies of P. ziziphi and for further references.
Parasitoids:
- Aphytis proclia, attacking: nymphs, adults
- Encarsia citrina, attacking: nymphs, adults, in Algeria, China, Hawaii, Egypt
- Encarsia lounsburyi, attacking: nymphs, adults, in China
- Habrolepis aspidioti, in Egypt
Predators:
- Chilocorus kuwanae, attacking: nymphs, adults, in China
- Chilocorus nigrita, attacking: nymphs, adults, in USA
- Cybocephalus nipponicus, attacking: nymphs, adults, in China
- Halmus chalybeus, attacking: nymphs, adults, in USA
- Leptodiplosis aonididiellae, attacking: nymphs, adults, in Morocco
- Rhyzobius lophanthae, attacking: nymphs, adults, in USA
- Telsimia emarginata, attacking: nymphs, adults, in China
Pathogens:
- Nectria aurantiicola, attacking: nymphs, adults, in Taiwan
- Nectria diploa, attacking: nymphs, adults, in Taiwan
- Nectria flammea, attacking: nymphs, adults, in Java
- Podonectria aurantii, attacking: nymphs, adults, in Brazil, Taiwan
- Podonectria cocciola, attacking: nymphs, adults, in Japan, Taiwan
Distribution
See Parlatoria ziziphi distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Comments
Parlatoria ziziphi probably originated in southern China (Longo et al., 1995) but has spread to all zoogeographical regions. It is found mainly in the tropics, but also extends into temperate regions.
Europe
Cyprus: present, no further details (CIE, 1964)
Former USSR
Caucasus: present, no further details (CIE, 1964)
Georgia, Republic of: present, no further details (CIE, 1964)
Transcaucasus:present, no further details (Danzig and Pellizzari, 1998)
France: present, no further details (Danzig and Pellizzari, 1998; Foldi, 2001)
Greece: present, no further details (Danzig and Pellizzari, 1998)
Crete: present, no further details (CIE, 1964)
Italy: present in the south (Longo et al., 1995; Danzig and Pellizzari, 1998)
Sardinia: present, no further details (Longo et al., 1995)
Sicily: present, no further details (Longo et al., 1995)
Malta: present, no further details (Danzig and Pellizzari, 1998)
Portugal: present, no further details (Danzig and Pellizzari, 1998)
Romania: present, no further details (Danzig and Pellizzari, 1998)
Spain: present in Alicante and Valencia (Amparo Blay Golcoechea, 1993)
Canary Is: present, no further details (Carnero Hernandez and Perez Guerra, 1986; Amparo Blay Golcoechea, 1993)
Switzerland: present, no further details (Tao, 1999)
Asia
Bangladesh: The Natural History Museum collection, London, UK
Bhutan: The Natural History Museum collection, London, UK
Cambodia: restricted distribution (Waterhouse, 1993)
China
Beijing: present, no further details (Tao, 1999)
Fujian: present, no further details (Tao, 1999)
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 (CIE, 1964)
Hong Kong: present, no further details (Tao, 1999)
Hunan: present, no further details (Tao, 1999)
Jiangsu: present, no further details (Tao, 1999)
Jiangxi: present, no further details (Tao, 1999)
Sichuan: present, no further details (Tao, 1999)
Yunnan: present, no further details (Ferris, 1950)
Zhejiang: present, no further details (Tao, 1999)
India: present, no further details (Tao, 1999)
Gujarat: The Natural History Museum collection, London, UK
Sikkim: The Natural History Museum collection, London, UK
Tamil Nadu: present, no further details (CIE, 1964)
West Bengal: present, no further details (CIE, 1964)
Indonesia
Bali: The Natural History Museum collection, London, UK
Irian Jaya: present, no further details (Reyne, 1961; CIE, 1964)
Java: present, no further details (CIE, 1964)
Sumatra: present, no further details (CIE, 1964)
Iran: present, no further details (Seghatoleslami, 1977; Abivardi, 2001)
Israel: restricted distribution (EPPO, 1999)
Japan: present, cannot read any further details (Kawai, 1980; Tao, 1999)
Honshu: present, no further details (CIE, 1964)
Kyushu: present; no further details (CIE, 1964)
Korea: present, no further details (Danzig and Pellizzari, 1998)
Korea, DPR: present, no further details (EPPO, 1999)
Korea, Republic of: present, no further details (EPPO, 1999)
Laos: present, no further details (Waterhouse, 1993; EPPO, 1999)
Lebanon: restricted distribution (EPPO, 1999)
Malaysia: restricted distribution (EPPO, 1999)
West Malaysia: present, no further details (CIE, 1964)
Sabah: present, no further details (CIE, 1964)
Myanmar: present, no further details (CIE, 1964; Waterhouse, 1993
Pakistan: present, no further details (EPPO, 1999; The Natural History Museum collection, London, UK)
Philippines: present, no further details (CIE, 1964)
Ryukyu Archipelago: present, no further details (EPPO, 1999)
Saudi Arabia: restricted distribution (EPPO, 1999)
Singapore: restricted distribution (Waterhouse, 1993)
South-East Asia: present, no further details (Danzig and Pellizzari, 1998)
Sri Lanka: present, no further details (Tao, 1999)
Syria: restricted distribution (EPPO, 1999)
Taiwan: present, no further details (Wong et al., 1999)
Thailand: present, no further details (CIE, 1964)
Turkey: present, no further details (Danzig and Pellizzari, 1998; Tao, 1999)
Vietnam: present, no further details (CIE, 1964; Waterhouse, 1993)
Africa
Algeria: present, no further details (Danzig and Pellizzari, 1998; Tao, 1999)
Benin: The Natural History Museum collection, London, UK
Cameroon: present, no further details (CIE, 1964)
Central African Republic: present, no further details (CIE, 1964)
Congo Democratic Republic: present, no further details (EPPO, 1999)
Congo: present, no further details (CIE, 1964)
Côte d'Ivoire: present, no further details (CIE, 1964)
Egypt: present, no further details (CIE, 1964; Danzig and Pellizzari, 1998)
Eritrea: present, no further details (CIE, 1964)
Ethiopia: present, no further details (EPPO, 1999; The Natural History Museum collection, London, UK)
Gambia: present, no further details (CIE, 1964)
Ghana: present, no further details (CIE, 1964)
Guinea: present, no further details (CIE, 1964)
Liberia: present, no further details (EPPO, 1999)
Libya: present, no further details (CIE, 1964; Danzig and Pellizzari, 1998)
Mali: present, no further details (CIE, 1964)
Mauritius: present, no further details (Williams and Williams, 1988)
Morocco: present, no further details (Danzig and Pellizzari, 1998; Tao, 1999)
Nigeria: present, no further details (CIE, 1964)
Senegal: present, no further details (CIE, 1964)
Sierra Leone: present, no further details (CIE, 1964)
Somalia: The Natural History Museum collection, London, UK
South Africa: present, no further details (CIE, 1964)
Togo: present, no further details (EPPO, 1999)
Tunisia: present, no further details (CIE, 1964; Danzig and Pellizzari, 1998)
Western Hemisphere
?Argentina: not recorded since 1938 (Claps et al., 2001a)
Buenos Aires: not recorded since 1938 (Claps et al., 2001a)
Córdoba: not recorded since 1938 (Claps et al., 2001a)
Santa Fe: not recorded since 1938 (Claps et al., 2001a)
Barbados: present, no further details (EPPO, 1999)
Bermuda: not recorded since 1949 (Hodgson and Hilburn, 1991)
Brazil
Sao Paulo: present, no further details (Watanabe et al., 2000a; Claps et al., 2001a)
Colombia: present, no further details (EPPO, 1999)
Cuba: present, no further details (CIE, 1964)
Dominica: restricted distribution (EPPO, 1999)
Dominican Republic: present, no further details (EPPO, 1999)
Guatemala: present, no further details (EPPO, 1999)
Guyana: present, no further details (CIE, 1964)
Haiti: restricted distribution (EPPO, 1999; The Natural History Museum collection, London, UK)
Jamaica: present, no further details (CIE, 1964)
Panama: present, no further details (EPPO, 1999)
Peru: restricted distribution (EPPO, 1999)
Puerto Rico: present, no further details (EPPO, 1999)
Trinidad and Tobago: present, no further details (EPPO, 1999)
USA
Florida: The Natural History Museum collection, London, UK
Hawaii: present on Oahu, Hawaii, Maui, Kauai and Molokai (Heu, 2002)
Mississippi: present, no further details (Ferris, 1937)
United States Virgin Islands: St Croix only (EPPO, 1999)
Venezuela: restricted distribution (EPPO, 1999)
Oceania
Australia: present, no further details (Williams and Williams, 1988)
Northern Territory: present, no further details (CIE, 1964)
Caroline Is: The Natural History Museum collection, London, UK
Guam: restricted distribution (EPPO, 1999)
Micronesia, Federated states of: present, no further details (EPPO, 1999)
Northern Mariana Islands: restricted distribution (EPPO, 1999)
Palau: present (Beardsley, 1966)
Pohnpei: present (Beardsley, 1966)