Orchamoplatus citri (Takahashi, 1940)
Australian citrus whitefly, Citrus whitefly
Aleuroplatus citri Takahashi, 1940
Biostatus and distribution
This adventive whitefly comes from Australia. It was first found in Auckland in October 2000 and quickly spread through the North Island and has reached the top of the South Island. It is mainly found on Citrus trees, but is also found on other trees including native species. It can reach high numbers on the underside of leaves.
Conservation status: Widespread on Citrus and occasionally found on other trees including native species.
Life stages and annual cycle
Australian citrus whitefly overwinter as larvae and pupae on the underside of host plant leaves. In spring, adults emerge from their puparium and start breeding on the young leaves.
Australian citrus whitefly has the same life stages and life cycle as the greenhouse whitefly, Trialeurodes vaporariorum. The adult whitefly has white wax covered wings and its yellow body is covered by a thin dusting of white wax. The adults are about 1.5 mm long and have a wing-span of about 3 mm. When the adults emerge, the yellow body colour can be seen and the wings are transparent, but soon the wings become covered with white wax. There are males and females in this species. Males may be seen sitting alongside females before mating.
Adult females lay eggs on the surface of the leaf in circles around where they are feeding. The oval eggs are laid on their sides but may have a peg at one end that is inserted into the leaf. They are pale at first, darkening over the next few days. The first larva to hatch from the egg has three pairs of legs and is usually called a crawler. It walks away from the egg and settles at a suitable feeding site, usually above or close to a leaf vein with phloem ducts (tubes that transmit nutrients from the leaf to other parts of the plant). The crawler is oval and develops two lumps of white wax along the centre of its body. There are four larval stages called instars. The larvae grow by moulting, (i.e. changing skin). The old skin splits on the upper dorsal side and the next larval instar pulls itself out and settles in the same place to feed. The third larval instar may also develop a white structure on its upper side. The fourth larval instar is ringed by fine wax filaments that are usually hidden by the sticky liquid covering the larva and the surrounding leaf. When the fourth instar larva reaches full size, it pupates inside the larval skin, which is now called a puparium. When the adult is almost ready to emerge, dark eyespots can be seen through the walls of the puparium. A T-shaped split occurs in the skin of the puparium and the adult pulls itself out. Its body and wings harden, and become covered in white wax.
Feeding and honeydew
Whitefly adults and larvae have sucking mouthparts. Long specially shaped rods called stylets are held in the sheath-like rostrum. When it wishes to feed, the whitefly moves the tip of the rostrum onto the surface of the plant leaf. The stylets are then gradually pushed into the plant and manoeuvred into the phloem (or nutrient transport vessels) of the plant. The whiteflies suck the plant’s sap, which is high in sugars and low in other nutrients. Whiteflies excrete the excess sugary liquid, which is called honeydew. In the larvae, the excess liquid is excreted into a structure called the vasiform orifice where it accumulates. When a droplet has formed, a tongue-like structure called the lingula flicks the droplet away from the larva. It can be flicked up to 2 cm away.
Honeydew makes the plant leaves sticky. Sometimes black sooty mould fungi grow on the sticky surfaces.
Australian citrus whitefly is the only species of whitefly in New Zealand found on its known host plants or other plants within the same genera. If Australian citrus whitefly is suspected to be on other plants, specimens of the whitefly puparium need to be examined by someone with taxonomic expertise in whitefly.
Australian citrus whitefly can be readily distinguished from other insects with scale-like stages, by the distinct appearance of the white adults, the circles of eggs, and the appearance of the larvae, especially the fourth stage that is surrounded by sticky honeydew.
No pathogens or parasitoids of Australian citrus whitefly are known in New Zealand.
In New Zealand five predators have been recorded feeding on Australian citrus whitefly. The two ladybirds and two lacewings feed on a variety of insects including whitefly, while the Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae) has only been found feeding on whitefly. It is probably an Australian species.
|Scientific Name||Common Name||Classification||Enemy Type||Reliability Index||Biostatus|
|Cybocephalus species 1||Citrus whitefly predator (Beetle)||Coleoptera: Cybocephalidae||predator||8||adventive|
|Drepanacra binocula (Newman, 1838)||Australian variable lacewing (Lacewing)||Neuroptera: Hemerobiidae||predator||10||adventive|
|Halmus chalybeus (Boisduval, 1835)||Steelblue ladybird (Beetle)||Coleoptera: Coccinellidae||predator||10||adventive|
|Micromus tasmaniae (Walker, 1860)||Tasmanian lacewing (Lacewing)||Neuroptera: Hemerobiidae||predator||10||adventive|
|Serangium maculigerum Blackburn, 1892||Citrus whitefly ladybird (Beetle)||Coleoptera: Coccinellidae||predator||10||adventive|
High numbers of Australian citrus whitefly are found on the underside of leaves of Citrus trees. It has also been found in high numbers on the underside of other cultivated trees and native trees such as Pohutukawa, Metrosideros excelsa (Myrtaceae).
Adult and juvenile whiteflies feed by inserting their stylets into the phloem, the nutrient transport vessels of the plant. The whiteflies suck the plant sap and feeding by large numbers of them can debilitate the plant. Plant sap is high in sugars and low in other nutrients. Whiteflies excrete the excess sugary liquid, which is called honeydew. This makes the plant leaves sticky. Sometimes black ’sooty mould’ fungi grow on the sticky surfaces.
|Common Name(s)||Scientific Name||Family||Reliability Index||Biostatus|
|Red horse-chestnut||Aesculus xcarnea Hayne||Sapindaceae||5||cultivated|
|New Zealand ash, Tapitapi, Tītoki, Tītongi, Tokitoki, Tongitongi, Topitopi||Alectryon excelsus Gaertn.||Sapindaceae||10||endemic|
|Mexican orange blossom||Choisya ternata Kunth||Rutaceae||10||cultivated|
|Meyer lemon, Chinese dwarf lemon||Citrus ×meyeri Yu. Tanaka||Rutaceae||10||cultivated|
|Tahiti lime||Citrus aurantiifolia (Christm.) Swingle||Rutaceae||10||cultivated|
|New Zealand grapefruit||Citrus grandis × reticulata||Rutaceae||10||cultivated|
|Lemon||Citrus limon (L.) Burm.f.||Rutaceae||9||naturalised|
|Myrtle-leaf orange||Citrus myrtifolia Raf.||Rutaceae||10||cultivated|
|Clementine, Mandarin, Tangerine||Citrus reticulata Blanco||Rutaceae||10||naturalised|
|Apple, Crab-apple||Malus ×domestica Borkh.||Rosaceae||10||naturalised|
|Houkūmara, Koheriki, Tākaka, Tātaka, Wharangi, Wharangipiro||Melicope ternata J.R.Forst. & G.Forst.||Rutaceae||7||endemic|
|Bartlett's rata||Metrosideros bartlettii J.W.Dawson||Myrtaceae||10||endemic|
|New Zealand Christmas tree, Hutukawa, Kahika, Pohutukawa, Pōhutukawa, Rātā||Metrosideros excelsa Sol. ex Gaertn.||Myrtaceae||10||endemic|
|Swamp maire, Maire tawake, Maire tawhake, Puka, Tuhuhi, Whāwhākou||Syzygium maire (A.Cunn.) Sykes & Garn.-Jones||Myrtaceae||10||endemic|
Australian citrus whitefly on native New Zealand plants are unlikely to warrant control. Australian citrus whitefly can sometimes reach high numbers on Citrus leaves. It is often difficult to control whitefly by using insecticides alone. In the home garden, heavily infest trees still produce large crops of fruit.
Non-insecticide controls include:
Removing overwintering leaves with large numbers of juvenile whitefly and burying or composting the leaves so that adults do not emerge.
Spraying the underside of leaves with soapy water will kill adult whiteflies.
Most insecticides will kill only adult or very young larvae of the cabbage whitefly. Eggs, older larvae and puparia are resistant to most insecticides. This means that a single application of most insecticides will not give adequate control of whitefly. Usually a sequence of applications is required to kill emerging adults before they lay many eggs, and to kill the young larvae when they hatch from eggs and before they grow and moult into larger larvae.
Commercial citrus growers should consult their industry guidelines or their Horticultural Supplier.
If insecticide sprays are used, they should be directed onto the undersides of leaves. In addition, chemicals that cause least harm to natural enemies should be selected.
Martin NA 1999. Whitefly: Biology, identification and life cycle. Crop & Food Research, Broadsheet No. 91: 1-8.
Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/
The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.