Oriental fruit fly

Oriental fruit fly (Bactrocera dorsalis) covers 4 previously described fruit fly species: Bactrocera dorsalis, B. papayae, B. philippinensis and B. invadens. They are now all known to be the same species.

Adults

• About the same length (approximately 7mm) as a common housefly but more slender and wasp-like in appearance.
• Clear wings.
• Generally, has a black back and a paler abdomen with a distinctive black T-shaped marking on the abdomen.

Eggs

• White to yellowish-white, long elliptical – like a sickle, and about 1–2mm long.

Larvae

• Maggots are creamy-white and up to 10mm long at full size (younger stages are smaller).

Pupae

• Varies in colour from white to yellow-brown.
• Roughly cylindrical.
• Approximately 5mm long.
• Typically found in the soil.

Plant stage and plant parts affected

• Fruiting plants, and fruit and vegetable produce (post-harvest).

Plant damage

As with other fruit fly species, females 'sting' the fruit when they lay their eggs inside. Larvae hatch from eggs and tunnel into the fruit. Considerable damage can occur inside the flesh before obvious signs can be seen on the outside of the fruit.

Fruit decaying bacteria are also deposited within the fruit during the egg laying process. These bacteria also contribute to fruit damage.

The most obvious signs of infestation are:

• small discoloured or water-soaked patches on the fruit skin, which develop from the 'stings'
• affected fruit rotting and often falling from the plant prematurely.

A distinctive feature of oriental fruit fly is that they can infest several kinds of fruit while it is still hard green or immature. Most other fruit fly species do not infest immature fruit.

The common Queensland fruit fly is a similar size but is a reddish-brown colour. It is not known to infest immature fruit. An expert is needed to identify oriental fruit fly under a microscope, so report any suspect exotic fruit fly species.

Widespread in Africa and Asia, and in some parts of the Pacific (Hawaii and French Polynesia).

It is closest to Australia in Indonesia, Timor Leste, and Papua New Guinea.

Oriental fruit fly has been recorded from nearly 500 host plant species in 81 plant families. Most fruit and above-ground vegetables are susceptible to attack.

There was an outbreak of oriental fruit fly (then known as papaya fruit fly) in Queensland in the late 1990s. During the eradication process, oriental fruit fly was found to breed in 35 host species and caused considerable damage to many types of fruit including coffee berries and green papaya/papaw.

• Adult female flies lay their eggs just under the skin of fruit and also deposit fruit decaying bacteria.
• Within 1–2 days, the eggs hatch into larvae (maggots) that feed on the decaying fruit, causing premature fruit drop.
• Depending on a range of factors, including temperature, after 6–35 days the larvae drop from the fruit to ground level, bury in the soil, and pupate.
• Flies emerge after another 10–12 days (depending on conditions), becoming sexually mature after 1–2 weeks.
• Flies live for several months; females are capable of laying eggs throughout their life span once mated.

Oriental fruit fly is one of the most damaging pests of tropical horticulture because of its wide host range and ability to attack some types of fruit while still green. It has been estimated that if exotic fruit flies such as oriental fruit fly were to establish on the Australian mainland, the resulting disruption and potential loss of domestic and international markets and income losses to growers would cost an estimated $2.1 billion.

In 1995 oriental fruit fly (then known as papaya fruit fly) was detected near Cairns and cost $33.5 million and took four years to eradicate at total cost to industry of $100 million.

Home gardeners would also be affected and suffer fruit and vegetable losses.

Oriental fruit fly could easily be brought into Australia by illegal importation of infested fruit.

Oriental fruit fly occasionally moves into the Torres Strait with monsoonal winds in the wet season and is eradicated as part of a highly successful, proactive eradication strategy.

Like most tropical fruit fly species, oriental fruit fly multiplies rapidly and can spread over large distances. All mainland states of Australia have climates and host crops suited to the establishment and spread of oriental fruit fly.

Fruit fly infestation of immature fruit can indicate the potential presence of oriental fruit fly.

There are several native pest species of fruit fly that will also damage fruit but usually only when fruit is ripe. If you have fruit and vegetables that have had no problems with fruit fly in the past, but are now infested with maggots, then it is possible that you have an exotic fruit fly species on your property.

Keep a look out and contact Biosecurity Queensland on 13 25 23 if you notice fruit fly damage of green or immature fruit or there are changes in the pattern of fruit fly damage to your crops.

• Protect your farm from emergency plant pests
• Understand good farm biosecurity
• Visit the farm biosecurity website

The nationally cost shared Exotic Fruit Flies in Torres Strait Eradication Program undertakes surveillance for eradication of oriental fruit fly and other exotic fruit fly species that may be seasonally dispersed from Papua New Guinea to the Torres Strait Islands with the summer monsoon season. Any incursions are eradicated immediately.

The program includes:

• trapping and identifying fruit flies for early detection
• using pheromone-based insecticide baits (blocks) to attract and kill male fruit flies
• using protein-based insecticide bait (spray) to kill adult female flies
• movement restrictions to prevent pest introduction and spread by movement of infested fruit and vegetables.

Oriental fruit fly is prohibited matter under the Biosecurity Act 2014.

Under Queensland legislation if you suspect the presence of oriental fruit fly, you must report it to Biosecurity Queensland immediately on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

If you think you have found oriental fruit fly, you must take all reasonable and practical steps under your control to minimise any associated risks. This is called a general biosecurity obligation (GBO).

Oriental fruit fly is also a declared far northern pest in Schedule 8 of the Biosecurity Regulation 2016. The far northern biosecurity zones (PDF, 333KB) have been established to prevent the spread of far northern pests.

Regulations are in place to restrict the movement of fruit and vegetables, plants and other plant material, soil and equipment (collectively called far northern pest carriers) which may harbour pests and diseases. You must apply for a biosecurity instrument permit to move any of these items out of the far northern biosecurity zones.

It is illegal to move a far northern pest such as oriental fruit fly, or far northern pest carriers without a biosecurity instrument permit:

• from far northern biosecurity zone 1 to a place outside of that zone
• or
• from far northern biosecurity zone 2 to a place outside that zone unless it is into far northern biosecurity zone 1.

You must observe movement restrictions if you are travelling to or around the Cape York Peninsula, or you live there.

For more information about biosecurity instrument permits, contact the Customer Service Centre on 13 25 23 or email qld.plantquarantine@daf.qld.gov.au.

Your cooperation in complying with these restrictions will help protect Queensland from exotic fruit fly outbreaks.