Queensland fruit fly

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

Bactrocera tryoni

Description of 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) that 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 7-10 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, apple, avocado, babaco, capsicum, carambola, casimiroa, cherry, citrus, custard apple, granadilla, grape, guava, kiwifruit, mango, nectarine, papaya, passionfruit, peach, pear, persimmon, plum, pomegranate, prune, quince, loquat, santol, sapodilla, tamarillo, tomato and wax jambu.

Damage

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

Adults lay eggs ('sting') 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.

To monitor fruit fly activity hang male lure traps under the shady canopy, where flies tend to rest. Check the number of flies trapped each week. The recommended trap contains a synthetic attractant combined with a fumigant insecticide. 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 options

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 as needed if approved on the affected crop.

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

Chemical registrations and permits

Check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your State/location. Always read the label. Always observe withholding periods.

Last updated 20 November 2012