Fruit fly Do’s and Don’ts

Fruit fly female biased BiotrapAndrew Creek
Development Officer, NSW DPI

Monitor fruit fly populations with traps as a guide to the fruit fly population trend in your orchard. There are traps that attract male flies only and also a newly developed female biased trap. Traps should be checked fortnightly. Trap data can be used to guide your protein bait spraying program and measure the baiting’s effectiveness. Fruit should still be routinely checked for fruit fly damage.

The female traps can also be placed densely on the boundaries of orchards to provide perimeter protection for up to three months before requiring servicing. (Pictured: The female Queensland fruit fly biased Biotrap® is effective for up to three months.)

Apply protein bait spray with a toxicant going into winter to reduce the number of fruit flies. Queensland fruit fly over-winters as an adult fly and requires a feed of protein to survive winter. It is the over-wintering population that starts the next generation in spring.

As temperatures rise in spring to over 16 °C at dusk, the fruit flies will be active. However, the female flies again require a feed of protein to mate and lay eggs. Spring is another good time to apply another protein bait spray with a toxicant. Killing off Queensland fruit flies before and just after winter is a great strategy to reduce fruit fly numbers.

Basic orchard equipment can be used to efficiently apply protein bait sprays. A length of hollow section steel mounted on a quad bike with nozzles on each side can easily cover 20 ha/hour.

Whilst baiting, growers should be aware that overseas maximum residue levels (MRLs) could be different from the Australian MRL. For example, in Taiwan the maldison MRL is 2 mg/kg, half that of Australia, and in the European Union it is 0.02  mg/kg, virtually zero. MRLs for abamectin have a similar trend with the Australian MRL being higher than many countries’ chemical residue tolerances.

Male annihilation technique (MAT) lures can be used in conjunction with protein baiting to have a greater reductive effect on Queensland fruit fly numbers. The MAT baits are laced with pheromone and insecticide. The baits only attract the male fruit fly and the insecticide kills them.

MAT baits are placed throughout the orchard at 10–20 per ha. MAT bait are more effective from spring through to late autumn. From late autumn, male flies are less actively mating as they prepare for winter.

Orchard sanitation is important. Queensland fruit fly in home fruit trees, around sheds and gardens, must also be managed for fruit fly. Queensland fruit fly has a very wide host plant range. Fallen or infested fruit should be destroyed. Fruit fly exclusion netting works well for home orchards and gardens. Feral and neglected fruit trees should be removed.

The key to managing Queensland fruit fly is monitoring their population, bait spraying and also orchard hygiene. Further information for commercially managing fruit fly can be found on the Riverina Local Land Services website