PEST
 
   NAME
     Whitefly, Snow flies
     Various Whitefly Species
 
   ORDER
     Hemiptera
 
   FAMILY
     Aleyrodidae

Description of the Pest
This is a small sap sucking moth-like insect up to 3mm long with winged adults that have a covering of fine white powder, hence the common name. The wings are folded flat over the body and males live for one month and females live up to three months. The eggs are laid on the underside of the leaf and the wingless nymphs are immobile, flattened-round scale -like with a fringe of waxy filaments. The nymphs are translucent to greenish, congregating on young plant tissue and both adults and nymphs suck sap and producing honeydew.   

There are several species such as Ash whitefly (Siphoninus phillyreae), Tobacco whitefly (Bemesia tabaci), Silverleaf whitefly and Spiralling whitefly (Aleurodicus disperses)

Greenhouse whitefly (Trialeurodes vaporariorum) 
This species of whitefly normally grow to 2mm long with two pairs of wings. Their colour is due to a covering of a fine white wax and the insect has a white-moth appearance. If disturbed the insects swarm and resettle on the plant quickly. The first nymphal stage is mobile and the later stage is scale-like with fine waxy marginal hairs. These nymphal stages produce honeydew, which encourages sooty mould. It is a persistent pest commonly found in glasshouses.

 Adult		 Appearance under the leaf	

The Hakea Whitefly (Synaleurodicus hakeae) is a small, moth-like up to 0.15mm wide with wings that have a powdery coating and produce flattened scale-like nymphs. Both adult and nymph gather together in colonies and suck sap.

Appearance and Distribution of the Pest
The eggs are laid during the spring and the adults tend to stay on the underside of the leaf until disturbed, when they fly in mass and may infect other plants. Many plants are only susceptible to this insect when cultivated under glass.

Life Cycle
This insect has a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.
White flies have a gradual metamorphosis, egg and four nymphal stages. One generation occurs from three to eight weeks and is dependant on the current weather. Hundreds of eggs are deposited on the underside of leaves in arch or circles each with a short stalk. 

 Eggs laid in a pattern	

After hatching the first nymphal stage wanders around on the leaf surface for several days. Then selects a place to suck sap where it goes through all nymphal stages emerging as an adult after the fourth stage. 

Period of Activity
This peat is found from tropical to temperate regions and is most active during warm weather. It is difficult to predict an infestation, as some years it is severe and other years it is absent. In glasshouse conditions it is often a problem and may extend outside the normal period of activity. They overwinter in the egg stage or find sheltered places to hide.

Damage Caused
Affected plants have leaves with yellowish to white mottling on the upper surface or with shiny secretions on new shoots or on the underside. Heavy infestations cause leaves to wilt and sooty mould to appear on the honeydew. Plant looses vigour and in some cases die.

 		 Tagetes erecta

Susceptible Plants
Whiteflies attack a wide range of plants affected by this insect, including Abutilon, Boronia, Hibiscus and Fuchsia species. Citrus, Vegetables, Ferns and certain weed species are venerable. Australian native plants are also attacked, such as the Hakea species.

Greenhouse whitefly (Trialeurodes vaporariorum) attacks a wide range of ornamental plants, weeds and vegetables including; Phaseolus (beans), Lycopersicon  (tomatoes), potatoes, Cucumis (cucurbits), Lactuca (lettuce), Dendranthema (Chrysanthemum), Dahlia and Hibiscus species. 
Several ferns, including Adiantum, Asplenium, Davallia, Nephrolepis, Onychium, Platycerium and Pteris species are attacked with nymphs congregating on the underside of the fronds, normally causing little damage. 

Rhododendron species are attacked by the Rhododendron White Fly (Dialeurodes chittendeni) causing yellowish mottled appearance on the upper surface of the leaf. 

Cultural Control
It is difficult to control with out the application of chemicals, though strong jets of water greatly disturb the colonies. Companion plantings with basil or other aromatic plants deters white flies or spray the plants with onion-garlic spray.
In an enclosed environment sticky fly paper can reduce numbers. When the nymphal stage is found an application of white oil will reduce numbers.

Biological Control
A parasitic wasp (Encarsia Formosa) attacks nymphal stages reducing numbers. Other predators include small birds, spiders, ladybirds and there lava, hover flies, damsel flies and mantids.

Chemical Control
Plants may be sprayed with Dimethoate, permethrin, bifenthrin or pirimiphos-methyl, but some insects have immunity to chemicals. The pest may also be sprayed with a mixture of white oil and nicotine sulphate or pyrethrum.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.