Spiralling whitefly

Adults

• Adults are tiny (2–3mm long) white flying insects that cluster together on plants and flutter around when disturbed.
• They are typically found feeding on the underside of leaves.

Nymphs

• Nymphs are similar in appearance to soft scale insects. They undergo 4 stages of development.
• In the first stage, nymphs are tiny (0.3mm long) and mobile. They crawl away from the eggs to find a feeding site.
• In the second and third stages, nymphs range in length from 0.5mm to 0.65mm and secrete waxy tufts or rods from their backs.
• In the fourth stage, nymphs produce more cottony white waxy material, with the waxy rods (up to 8mm long) extending upward and outward from their backs.

Eggs

• Eggs are tiny (0.3mm long), oval-shaped and yellow to tan in colour.
• They are laid on a short stalk that is attached to the plant. Deposits of waxy secretions around the eggs form a distinctive spiral arrangement.

Plant stage and plant parts affected

The leaves of plants of all ages can be affected by spiralling whitefly. Fruit can also be affected.

Plant damage

Spiralling whitefly mostly feed on the underside of leaves.

Nymphs and adults produce a sugary secretion called 'honeydew' and waxy material.

In heavy infestations, mould grows on the honeydew, giving leaves a black, sooty appearance.

Sooty mould, in combination with leaf damage, reduces the plant's ability to photosynthesise. It weakens, but rarely kills, the plant.

In the absence of natural predators, spiralling whitefly multiply very quickly, producing thousands of individuals on a single plant. Direct feeding damage from large numbers of whitefly can cause premature leaf fall or yellowing and curling leaves.

Spiralling whitefly looks like the closely related coconut whitefly (Aleurodicus destructor), which is widely distributed in South-East Asia and Australia. Coconut whitefly is a minor pest of some plants (including coconut, custard apple, banana and acacia) but is not considered a serious pest.

It is difficult to tell the difference between coconut and spiralling whiteflies with the naked eye. An expert is usually required for accurate identification.

Spiralling whitefly is believed to have originated in the wet tropics of Central and South America. It established in Hawaii in 1978 and spread rapidly through the Pacific. It is now found in most tropical countries of the world and some subtropical and temperate countries.

Spiralling whitefly was detected in Australia in the late 1990s and is now established in tropical coastal Queensland at locations from the Torres Strait to Bundaberg. It is also known to occur in the Northern Territory.

Spiralling whitefly infests:

• a broad range of horticultural plants including banana, citrus, papaya, mango, custard apple, guava, tomato, capsicum and eggplant
• many ornamental species, shade trees and weeds.

It has been recorded on more than 100 plant species but is most commonly found on poinsettia and Acalypha.

• Each spiralling whitefly egg hatches into a tiny active first-instar nymph that is roughly the same size as the egg.
• The first-instar nymph crawls out of the egg and over the foliage of the host plant, then moults into a sedentary stage (second, third and fourth stages). It attaches to the underside of a leaf, where it sucks nutrients from the plant.
• The second- to fourth-instar nymph has no visible legs and progressively produces more 'wax' and sugar secretions.
• The fourth-instar nymph continues feeding while attached to the leaf. It then stops feeding while it develops internally before emerging as an adult.
• The time from egg to adult can be less than 3 weeks in summer, but is usually longer in cooler conditions.
• Adults can live for 2 weeks. The female whitefly can lay large numbers of eggs.

Spiralling whitefly is a pest of a wide range of host plants and can affect commercial and recreational growers.

• Direct feeding (where numbers are high) can result in economic damage to crops because the feeding leads to:
  • premature leaf drop
  • reduced plant vigour
  • reduced yield.
• Cosmetic, indirect damage can arise from the:
  • production of honeydew, which encourages the growth of sooty mould
  • white waxy material produced by the nymphs sticking to plants.
• Infestation can affect access to domestic and international trading markets.
• Backyard growers can be impacted by:
  • reduced crop yields
  • unappealing appearance of ornamental plants.

The adults are relatively weak flyers, although when assisted by wind they can spread moderate distances.

Long-distance spread is usually human-assisted, for example by:

• hitchhiking on clothing and equipment
• being transported with plant material such as pot plants.

Check common host plants. You may see adults flying around host plants during calm, still times of the day (such as at dawn and dusk). Alternatively, if you shake an infested plant, the adults will fly then quickly resettle.

You can also use yellow sticky traps and sticky rolls to monitor adults and other flying insects.

If you think you have seen spiralling whitefly outside of the known infested areas, report it using one of these methods:

• report online
• call Biosecurity Queensland on 13 25 23
• call the Exotic Plant Pest Hotline on 1800 084 881.

Use these resources to help protect your farm from plant pests and diseases:

• Protect your farm
• Farm biosecurity

• Try to remove early infestations manually by hosing or wiping down the infested area to remove the crawlers and the waxy material. Alternatively, remove the plant tissue where crawlers are attached. Dispose of wipes and plant material in a sealed bag in general waste. Do not compost or dispose of infested plant material in garden waste.
• Natural enemies of spiralling whitefly such as lacewings, ladybirds, hoverflies (syrphids) and parasitoid wasps (Encarsia) can provide control.
• Do not try to control spiralling whitefly using insecticides. Overseas experience shows that spraying with insecticides has little long-term impact on the pest and usually increases the problem by:
  • destroying biological control agents (natural enemies)
  • increasing insecticide resistance in whitefly populations.

There are no legal requirements for the movement of spiralling whitefly host plants within Queensland.

However, the presence of spiralling whitefly can affect the movement of plants and plant products interstate.

If you are planning to move plants and plant products from Queensland to other states or territories, check with the destination states/territories before consigning.

Find out more about restrictions on moving plant material, soil and related equipment from Queensland to other states or territories.