PEST
 
   NAME
     Queensland Fruit Fly
     Dacus tryoni
 
   ORDER
     Diptera
 
   FAMILY
     Tephritidae

Description of the Pest
The Queensland Fruit Fly is an Australian native pest. The insect is reddish brown with yellow markings on the thorax, and grows up to 7mm long. Wings are clear, with a dark frontal rib. The female has a prominent ovipositor. Larvae are creamy-white legless maggots, 8-9mm long, with bodies tapering towards the heads.

Appearance and Distribution of the Pest
Fruit flies are found throughout the world; many, like the Queensland Fruit Fly, are a major pest. The Queensland Fruit Fly is found throughout the eastern States of Australia. Airline travel has been the biggest cause of contamination; the Queensland Fruit Fly extends further south along the Australian east coast every year. Fruit flies are not strong fliers but can traves substantial distances with the assistance of wind or the lava can be transported in contaminated fruit to new regions.

Life Cycle
This insect has a Holometabolous life cycle, ie. When metamorphosis is observed during the pupal stage.
Up to five generations are produced annually. Maggots feed on the pulp of the host fruit before falling to the ground, where they pupate in the soil for 2 weeks before emerging as adults. Adults feed on honeydew.

Period of Activity
Most active during from late Spring through Summer; with multiple generations appearing, large numbers may have built up by mid-Summer. They may over-winter as inactive adults, but are killed off during cold winters. Hot dry weather also reduces numbers of emerging adults.

Damage Caused
Discoloration appears on the surface of the fruit, around the puncture-wound caused by the female’s ovipositor. Rot occurs around the puncture. Maggots typically burrow deep into the flesh of the fruit; damage may not be apparent until the fruit is cut. Infested fruit may ripen early and fall prematurely. Damage varies according to the degree of infestation and the climatic conditions. Uncontrolled infestations may be commercially disastrous for orchards.

Susceptible Plants
A wide range of fruit is attacked: avocados, citrus, bananas, figs, stonefruit, pome fruit, persimmons, grapes, etc. Queensland Fruit Fly also attacks rainforest fruit such as Moringa oleifera.

Cultural Control
Control methods for commercial growers, according to the region: this usually involves a combination of sanitation, quarantine and application of insecticides. Some climatic areas do not permit continued development of fruit flies. Early-ripening varieties may be harvested before fly populations build up. Trees may be pruned to manageable sizes to facilitate spraying and picking; soil around trees may be cultivated to keep it weed-fry and disturb pupating larvae. Mesh enclosure of host plants (<2mm diameter) prevent contamination.

Hygiene is the best method for control, it is important to pick up any fallen fruit and dispose of it by feeding to farm animals or placing it in a bucket of water for at least ten days. Avoid placing fruit or vegetable scraps in a compost system that is not generating heat, as the fruit fly will lay eggs in it. In an orchid situation it is advisable to allow fruit eating animals such as chooks, sheep or geese to roam the floor to clean up the fallen fruit.
Fruit that remains on the plant after it is ripe should be removed as it is susceptible to attack, tomatoes are particular attractive for fruit fly and should not be planted near the orchid.

Biological Control
Parasitic wasp’s praying mantis, assassin bugs, spiders and birds help to control native infestations. Commercial fruit may be protected by baits or lures. Home made bates such as a plastic bottle half filled with a yeast-smelling product such as ginger beer and perforated to allow access for the fly can be hung fro a tree. Gamma-sterilized flies may be released to breed with wild populations, producing non-viable eggs.
Using synthetic pheromone traps (“Dakpots”) to monitor the activity of males will give you no protection.
Home gardeners can cover small trees with nets that are fruit fly proof, but this may be difficult to manage and hard to pick the fruit.

Chemical Control
Maldison helps to reduce the numbers of males, but fails to satisfy quarantine conditions. Cover sprays are typically systemic insecticides that kill eggs and larvae in the fruit. Penetrative sprays are effective in areas where baits are not. Note that some chemical treatments (fenthion or dimethoate) have undesirable side effects (eg leaf drop, or toxicity to birds and natural predator).

Fruit may be dipped to comply with quarantine conditions after harvesting.

Fruit may be dipped to comply with quarantine conditions after harvesting.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.