David Astridge & Harry Fay

Description

	Larvae of Queensland fruit fly with damaged (darker) areas of fruit. Note the black moth parts in the head of each larva.
	Adult Queensland fruit fly (Bactrocera tryoni ).

Adult

The adult is wasp-like, red-brown with yellow marks, and about 8 mm long. Unlike cucumber fruit fly there is no central yellow mark down the length of the dorsal surface of the thorax between the wings. Fruit flies hold their wings outstretched in a horizontal position when walking. They flick them in a characteristic manner.

Immature stages

The female pierces (stings) the maturing fruit and lays a clutch of white, banana-shaped eggs just below the surface. Hatching takes place after two to three days and the resulting larvae are white carrot-shaped maggots (about 7 mm long when mature) which tunnel in the flesh. They carry bacteria that aid in fruit breakdown. The mature larvae can 'jump' by curling into a 'U'-shape and then rapidly straightening.

Life history

Larvae mature in seven to 10 days in summer and emerge from the fruit to pupate in the soil. The pupal stage lasts about 10 days. The life cycle takes about 2.5 weeks during summer. The adult flies congregate on foliage and fruit to feed on bacterial colonies and later to mate. These bacterial colonies are more plentiful under humid conditions.

Distribution

Queensland fruit fly is a native pest occurring throughout eastern Australia.

Host range

Queensland fruit fly infests both indigenous and introduced fruits. Commercial varieties affected include abiu, apples, avocados, babaco, capsicum, carambola, casimiroa, cherries, citrus, custard apples, granadilla, grape, guavas, kiwifruit, mangoes, nectarines, papaya, passionfruit, peaches, pears, persimmons, plums, pomegranate, prunes, quinces, loquats, santol, sapodilla, tamarillo, tomatoes and wax jambu.

Management

Importance

Major and frequent pest. Activity is greatest in warm humid conditions and is particularly important where tree ripened fruit are concerned.

Damage

Adults lay ('sting') eggs in the fruit and the larvae feed in the flesh. Affected fruit are readily recognised since rots develop rapidly and the skin around the sting marks becomes discoloured. Queensland fruit fly damage is more severe during mid and late summer than at other times. Large numbers of flies can be expected after good falls of summer rain; fruit flies become active after periods of rain or high humidity.

Action level

If an orchard is being treated frequently, e.g. every two weeks for fruitspotting bug control, then fruit fly control will rarely be necessary since the insecticide used for bug control will suppress fruit fly populations. Fruit fly activity can be monitored by hanging male lure traps under the shady canopy, where flies tend to rest. The number of flies trapped should be checked each week. The recommended trap contains a synthetic attractant (cue-lure) combined with a fumigant insecticide (dichlorvos). Growers need to seriously consider whether fruit flies are causing sufficient damage to warrant spraying. A number of traps (one per hectare) should be hung in the middle of each large orchard block of 5.0 ha or more according to manufacturer's instructions. Inspect traps at weekly intervals from the end of flowering and until the completion of harvesting. Control maybe necessary as soon as two flies per trap per day are caught.

Control methods

Cultural

Fruit flies become active after periods of rain or high humidity. Sprays for fruit fly control may not be necessary in dry seasons.

Do not allow fallen fruit to accumulate under trees.

Biological

While there are a number of parasitoids, these kill the insect in the pupal stage and are therefore of little use in preventing damage. However, they do help to reduce the next generation of flies, particularly in isolated or marginal fly areas.

Chemical

Apply cover sprays of fenthion or dimethoate as needed if approved on the affected crop.

Spinosad bait concentrate is approved on various tree, fruit, vine and vegetable crops for spot spraying.

Recommended chemicals

Dimethoate, fenthion and spinosad bait concentrate.

Note: This information was correct at the time of publication. However, it is the user's responsibility to ensure that registered agricultural chemicals are used in accordance with legal requirements. (See Further information). Always read the label.

Further information

• Contact the DPI&F Business Information Centre on 13 25 23 - local call 8 am to 6 pm Monday to Friday (non-Queensland residents phone 07 3404 6999). E-mail: callweb@dpi.qld.gov.au
  
• Contact the DPI&F bookshop on 07 3239 3772 or  DPI&F Shop-online or at some DPI&F offices throughout Queensland for the DPI&F publications
  
• Infopest CD-ROM contains current national information on registered agricultural chemicals and is available from Infopest, DPI&F, GPO Box 46, Brisbane Qld 4001 or by email from infopest@dpi.qld.gov.au
  

Recommended reading:

Hely, P.C., Pasfield, G. and Gellatley, J.G. 1982, Insect pests of fruit and vegetables in New South Wales Inkata Press, Sydney.

Other contacts: 

Growcom on 07 3620 3844

Growers interested in the production of minor tropical fruits can join their local branch of the Rare Fruits Council and subscribe to their newsletter. Contact the Rare Fruits Council at PO Box 1375 Aitkenvale 4814

The DPI&F library provides a personalised information search service that may be useful for producers seeking information on minor and exotic crops

DPI&F InfoResearch on 07 3239 6989.

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Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.

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Last updated 19 December 2005