Winter and the Queensland Fruit Fly – July 2019

Despite winter, sizable numbers of Queensland Fruit Fly (QFF) adults could still be alive in warm refuges such as lemon trees near houses. These are the flies that will start the QFF population explosion next spring. Now that it is cold in the Goulburn Murray Valley (GMV), fruit flies are doing two things:

  1. Searching for food and water to build up reserves for survival during periods of immobility caused by the cold; and
  2. Looking for refuge from the cold, wind, rain and predators.

Food-based traps and baits based on protein, can still be effective, especially during warm parts of the day. Such traps and baits can control hungry fruit flies in the backyard and orchard. Place traps in warm spots — e.g. in the lemon tree near the house or chook yard. Don’t forget that the removal of unwanted QFF host plants is a very useful and effective way of controlling future fruit fly populations.

Advice to commercial growers

Orchard hygiene, disposal of unwanted fruit, food-based traps and fruit fly baits are useful techniques for fruit fly management in commercial orchards. The number of fruit flies trapped in the GMV trapping grid dropped sharply in rural locations from more than three QFF per trap in mid-April to less than one QFF per trap by mid-May. Trapping results in rural locations of the GMV for 2019 showed further decreases. During the first two weeks of June 2019 only 21 QFF were trapped from a total of 250 rural sites (a rate of 0.08 QFF per trap per fortnight). This is very low, however not all QFF are dead due to the cold weather. They are smart enough to have built up energy reserves with protein rich feed (usually wild yeasts, fungi and bacteria found naturally) and to have moved to warm refuges away from rain, wind, cold and predation.

Fruit fly populations

The 2018/2019 QFF population was significant in that it was the lowest it has been since the beginning of the GMV QFF Area Wide Management (AWM) project. Weather played a part in this decrease but was not the sole factor. The AWM project played a significant role along with increased public awareness and tree removal programs. It is now very important that this success be maintained with continued and improved diligence in home gardens, commercial areas, council and Crown lands and orchards. Applications are still being accepted for the removal of unmanaged orchards.

If you are interested, please contact the GMV Queensland Fruit Fly Office by phoning (03) 5871 9222 or emailing for more information.