Spiraling whitefly

Spiraling whitefly fact sheet [English]

Spiraling Whitefly - Background Information and Control Measures

The spiraling whitefly is native of the Caribbean Region and Central America where it is not regarded as a pest because it is kept under control by a number of native predatory insects and tiny parasitic wasps.

Spiraling whitefly was first discovered in Hawaii in 1978 and from there spread through the pacific islands and then westwards to Asia (1987) and Africa (1992). It was found in north Queensland (Cape York) in 1995 and Cairns in 1998.

Three species of predatory ladybirds and two parasitic wasps (Encarsia spp.) were introduced to Hawaii in 1979 and 1980 leading to large reductions (80-99%) in population levels of the pest. Since then the parasitic wasps have been introduced into most of the other infested countries with similar results including the city of Cairns in Australia.

The whitefly pest was first detected in Darwin in March 2006. Within days some of the known parasitic wasps (Encarsia spp.) were collected from Cairns and sent through to Darwin by Queensland Department of Primary Industry and Fisheries. These were held in the laboratory by the NT Department of Regional Development, Primary Industry, Fisheries and Resources (RDPIFR).

The parasitic wasp lays its eggs in the immature whiteflies and the wasp larvae develop within the whiteflies. When the wasp larvae are full grown and pupate, the whiteflies die, and adult wasps emerge from the pupae.

The parasitic wasps were introduced to areas in Darwin as a biological control agent to help combat the whitefly pest. The parasites released proceeded to attack their whitefly host, and continued to reproduce and spread in the wild.

One of the parasitic wasps (Encarsia sp.) is now established in a number of areas around Darwin where infestations have been reported. The wasps have bred up to large numbers and will now disperse naturally to other whitefly infested areas. This spread will become more rapid as the parasite populations increase as they attack the current high numbers of whiteflies. Whitefly populations have already been reduced significantly in most areas where the parasitic wasp has been released and established.

The parasites are not available commercially nor are they being bred in culture, as once they are established it is generally not necessary to make further releases. (They should not be confused with the related species Encarsia formosa obtainable from biological control companies for the control of a different pest, the greenhouse whitefly).

While the parasite will spread naturally, RDPIFR is assisting the spread by collecting parasites from field collected whiteflies and releasing these parasites in new areas. (As stated earlier they are not being bred in captivity by RDPIFR. Allowing the parasitic wasp to breed in the wild is more efficient)

In areas where the parasite is established many of the whiteflies will have the immature stages of the parasite inside them. If a new infestation of spiraling whitefly has been detected in an area for the first time it may not yet have the parasite and it may assist control by taking infested leaves from known whitefly infested areas to the new site.

Once the parasite is introduced to an area infested with whitefly, it will take the parasite several months to establish and begin reducing pest numbers. However in the long term it is expected that the wasp parasite will dramatically reduce the numbers of the whitefly pest in new areas, as it has done in areas where it has previously established.

In the short term growers may want to spray for the whitefly using products recommended in the recent fact sheet and advert put out by the department. There are many products containing the oils and potassium soaps recommended and the local suppliers can give advice on the ones they have in stock.