**Queensland Fruit Flies** (**QFF**, *Bactrocera tryoni*) are arguably the most serious insect pest of **commercial fruit and vegetable crops** in Australia and a major quarantine concern globally. The conflict is severe economic loss: the female fly punctures ripening fruit to lay eggs inside. The hatching larvae (**maggots**) feed on the flesh, causing the fruit to quickly **rot, collapse, and drop prematurely**, making the entire crop unusable for market.
Taxonomy and Classification
QFF belongs to the order Diptera (Flies), family Tephritidae (True Fruit Flies). They undergo complete metamorphosis. They are highly polyphagous, attacking a vast range of hosts including mangoes, stone fruit, citrus, tomatoes, and capsicum. They are extremely difficult to control due to their rapid reproduction and ability to fly long distances.
Physical Description
Adult QFF is small, 5-8 mm long.
- **Appearance (Key ID):** Reddish-brown body with prominent **bright yellow markings** on the thorax, clear wings, and large eyes. They resemble a small wasp more than a house fly.
- **Larva (Key ID):** Small, creamy-white, legless maggot found exclusively inside infested fruit.
- **Damage Sign (Key ID):**
- **Stings/Punctures:** Pin-prick size oviposition marks (stings) on ripening fruit.
- **Rot:** Soft, brown, rotten patches developing around the sting mark, often with maggots present.
- **Premature Drop:** Fruit dropping from the tree/vine before it is ripe.
- **Conflict:** Severe crop loss and high-cost quarantine restrictions.
Distribution and Habitat
QFF is endemic to eastern Australia and has spread across the continent. Their habitat is fruit-producing trees, orchards, and suburban gardens where they can find continuous hosts throughout the year.
Behavior and Conflict
The conflict is dominated by the hidden damage and regulatory costs.
- **Quarantine Barrier:** Its presence prevents movement of fresh produce across state and international borders unless the produce undergoes expensive treatment (e.g., cold storage, irradiation).
- **Hidden Infestation:** The initial damage is not always visible, allowing the larvae to develop and the fruit to be inadvertently shipped, leading to new outbreaks.
- **Chemical Resistance:** Repeated, widespread insecticide use has led to concerns about resistance development, complicating control efforts.
Management and Prevention
Control is integrated pest management (IPM), utilizing a community-wide strategy.
- Use pheromone and food-lure traps to monitor fly presence and population density.
- Apply specific **protein bait sprays** containing a toxicant. The flies (which require protein) feed on the bait and are killed before they can lay eggs.
- **Sanitation:** Collect and destroy (boil, freeze, or solarize) all infested and fallen fruit immediately.
- **Exclusion:** Netting or bagging individual trees or fruit clusters.
- Releasing mass-reared, sterilized male flies into the wild population to mate with females, resulting in no offspring.
Conservation and Research
QFF is managed as a high-priority invasive and economic pest. Research focuses on optimizing SIT release programs, developing more effective and targeted lures, and breeding fruit varieties with greater resistance to fly puncture.