Queensland Fruit Fly Outlook – May 2022

This information has been commissioned by the Goulburn Murray Valley (GMV) Fruit Fly Program and is funded by the Victorian Government. Use of this material in its complete and original format, acknowledging its source, is permitted, however unauthorised alterations to the text or content is not permitted.

Fruit fly trapping data and insights

The number of Queensland fruit fly (Qfly) trapped in the Goulburn Murray Valley (GMV) began to decline through autumn. Fruit fly activity did proceed however, despite lower numbers being trapped. This is because temperatures started to became too cold for trapping but not be cold enough to stop mating, egg-laying and larval development despite temperatures being milder than normal for this time of year.

The suppression of fruit fly activity in autumn impacts numbers next season, making it easier to manage next spring which is why fruit fly control in autumn is an important aspect of management of the pest.

Fruit fly trapping data have been collected throughout the GMV for at least five fruit fly seasons (i.e. from 1 July to 30 June). Fruit fly activity, based on the numbers of trapped fruit flies, varies throughout the year. March is most often the month where most fruit flies are trapped and these trappings correspond with the ripening of large volumes of pome and stone fruit in commercial orchards. It also corresponds with the most benign weather conditions for fruit fly survival and proliferation. Flies emerging from fruit infested at this time of year (emergence of these flies will be in April) typically are not attracted to traps due to the cool weather. It will seem that flies are in decline but that’s not necessarily the case. These flies ‘hibernate’ where their able to over winter as adults. The greater the numbers of these flies overwintering the greater the problem will be in spring and, hence, next cropping season if not managed adequately.

Seasonal weather impacts

Temperatures in early 2021/22 were slower to rise than in previous years (early October to mid-December). This caused a delay in fruit fly population build-up in late 2021. With the exception of early February 2022 rainfall has been higher in 2021/22 than most other years. Corresponding higher humidity and lower desiccation in 2022 has meant there was negligible adverse climatic impact on fruit flies and the fruit they infested.

Late autumn sees fruit flies build up before the cold snap which helps them survive the winter and start their new season of fruit damage next spring. This is where orchard (or post-harvest) hygiene becomes important. Growers and property owners have the ability to break the fruit fly cycle by successfully cleaning up orchards, home gardens and nearby untended land of potential fruit fly host material: No fruit = No fruit fly.

Extra vigilance required

The below sites were considered autumn ‘Hot Spots’. It is important that orchards in these areas take precautions to reduce the ability of fruit fly to infest fruit and to survive in them.

The below sites have the potential to become sites from which large numbers of Qfly could establish and spread, so it is important that members of the GMV community who have gardens and orchards in these areas take precautions to reduce the ability of fruit fly to infest fruit and to survive in them.

Fruit fly control and management for commercial growers

Commercial growers in or near the above locations should also be aware of fruit flies being nearby and implement fruit fly control:

• • Monitor fruit fly traps for Qfly population presence and build-up
  • Check fruit for fruit fly infestation
  • Weekly baiting
  • If the fruit fly problem is too severe, use approved pesticides
  • Carry out after harvest clean-up
  • Keep house gardens clean, too as well as creek banks, compost heaps, roadsides
  • Notifying authorities of nearby untended/ feral fruiting plants
  • Ensure stock of traps, lures, toxicants, approved pesticides, baits, application equipment, etc are in good supply and good condition.

Weather outlook and its impact on future fruit fly activity

Normally, fruit fly activity declines in late April so that any eggs or larvae in fruit or pupae in the ground in the GMV past mid-April will die due to the cold.

But weather conditions for April and May 2022 were not significantly damaging to fruit fly survival and activity, indicating the fruit fly season will extend further into late autumn and early winter than usual. Fruit fly activity in the form of mating, egg-laying and consequent fruit damage followed by adult emergence is more likely in milder conditions at this time of year.

Goulburn Murray Valley Fruit Fly Program

For assistance in managing Qfly, contact the Project Coordinator at the GMV Fruit Fly Office by phoning (03) 5871 9222 or email gmvfruitfly@moira.vic.gov.au. For more information on fruit fly control and area wide management strategies visit www.fruitflycontrol.com.au

This report was produced and supplied by Janren Consulting Pty Ltd for the purpose of the GMV Fruit Fly Program. The GMV Fruit Fly Program is supported by the Victorian Government.