INTERESTING INSECTS

By N A Martin (2018)

Australian citrus whitefly, Citrus whitefly

Aleuroplatus citri Takahashi, 1940

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.

Diagramme of the life cycle of the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). Creator: Based on figure 20 from Crop & Food Research Broadsheet 91. © Plant & Food Research. [Image: 3BG]

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, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCB]

Adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCC]

Adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae): note the circular groups of young eggs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC9]

Adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae): note the circular groups of eggs Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCA]

Young and older eggs of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBP]

Eggs and first instar (stage) larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae) : note the white wax on the larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBT]

Eggs and, first and second instar (stage) larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae) : note the white wax on the first instar larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBV]

First, second and third instar (stage) larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae) : note the white wax on the first instar larvae and the white material on the third instar larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBU]

Older larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae) : note the white material on the third instar larvae, those with white bodies are about to moult. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBX]

Larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae): note the sticky liquid arround the older larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBZ]

Large larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae): note the ring of wax filaments visible arround some fourth instar (stage) larvae and the sticky liquid arround them. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC1]

Egg shells and fouth instar larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae): note the sticky liquid arround the larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC2]

Full and emptey puparia of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae): note the eye spots in some of the unemerged puparia. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC4]

A recently emerged adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae): note the pale wings that have not got their full amount of wax. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC5]

A recently emerged adult and its empty puparium of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae):. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC3]

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.

Adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCC]

Adult Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) laying eggs on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae): note the circular groups of young eggs. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TC9]

Egg circles of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBQ]

Larvae of Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae): note the sticky liquid arround the older larvae. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBZ]

Overwintering Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCG]

No pathogens or parasitoids of Australian citrus whitefly are known in New Zealand.

Predators

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.

Adult male Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae): note the large pronotum, the first segment behind the head. Creator: Tim Holmes. © Plant & Food Research. [Image: 2MMN]

Adult female Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae): note the all black head and pronotum (the first segment behind the head). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2MNX]

Cocoons of Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae) on a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae) infested with Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae): note the clear space around each cocoon. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBD]

Cocoons of Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae) on a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae) infested with Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae): note the clear space around each cocoon. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBE]

Larva of Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae) feeding on Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBF]

Larva of Citrus whitefly predator, Cybocephalus species 1 (Coleoptera: Cybocephalidae) feeding on Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBG]

Adult citrus whitefly ladybird, Serangium maculigerum (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 163Z]

Adult citrus whitefly ladybird, Serangium maculigerum (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 163X]

Two eggs of citrus whitefly ladybird, Serangium maculigerum (Coleoptera: Coccinellidae) on a citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 166V]

Large larva of citrus whitefly ladybird, Serangium maculigerum (Coleoptera: Coccinellidae), on citrus leaf. Creator: Tim Holmes. © Plant & Food Research. [Image: 164F]

Larva of citrus whitefly ladybird, Serangium maculigerum (Coleoptera: Coccinellidae). Creator: Minna Personen. © Plant & Food Research. [Image: 164L]

Adult steelblue ladybird, Halmus chalybeus (Coleoptera: Coccinellidae), about 4 mm long. Creator: Tim Holmes. © Plant & Food Research. [Image: 15VZ]

Mature larva of steelblue ladybird, Halmus chalybeus (Coleoptera: Coccinellidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 15W1]

Adult Australian variable lacewing, Drepanacra binocula (Neuroptera: Hemerobiidae), from a colony of shining spleenwort whitefly, Trialeurodes asplenii (Hemiptera: Aleyrodidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2IL5]

Adult Australian variable lacewing, Drepanacra binocula (Neuroptera: Hemerobiidae), from a colony of shining spleenwort whitefly, Trialeurodes asplenii (Hemiptera: Aleyrodidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2IL8]

Australian variable lacewing larva, Drepanacra binocula (Neuroptera: Hemerobiidae) feeding on citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2IQX]

Australian variable lacewing larvae, Drepanacra binocula (Neuroptera: Hemerobiidae) feeding on citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2IQV]

Adult Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FL]

Larva of Tasmanian lacewing, Micromus tasmaniae (Neuroptera: Hemerobiidae). © Plant & Food Research. [Image: 3FO]

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.

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tītoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBH]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tītoki, Alectryon excelsus (Sapindaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBI]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Pohutukawa, Metrosideros excelsa (Myrtaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBJ]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Pohutukawa, Metrosideros excelsa (Myrtaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBK]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Bartlett's rata, Metrosideros bartlettii (Myrtaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBL]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Bartlett's rata, Metrosideros bartlettii (Myrtaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBM]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of leaves of Bartlett's rata, Metrosideros bartlettii (Myrtaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TBN]

Overwintering Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCG]

Overwintering Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCE]

Overwintering Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCF]

Overwintering Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a leaf of Tahiti lime, Citrus aurantiifolia (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCH]

Australian citrus whitefly, Orchamoplatus citri (Hemiptera: Aleyrodidae) on the underside of a young leaf of Meyer lemon, Citrus ×meyeri (Rutaceae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2TCB]

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.

Insecticides

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.