Queensland Fruit Fly Outlook – March 2021

Queensland Fruit Fly Goulburn Murray Valley Outlook – March 2021

This information has been commissioned by the Goulburn Murray Valley (GMV) Fruit Fly Project and is funded by the Victorian Government’s Managing Fruit Fly Regional Grants Program. 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.

Current trends in fruit fly populations

• Trapping data show that the 2020/21 fruit fly season has been particularly bad and is likely attributed to the onset of the La Niña weather pattern in March 2020 which is highly favourable for Queensland fruit fly proliferation.
• Currently, captures of fruit fly are slowing down in URBAN areas but are on the rise in RURAL locations of the Goulburn Murray Valley.
• As daily temperatures start to get cooler, conditions become ideal for fruit fly to mate and lay eggs.
• Eggs laid during February will become a new generation of pest fruit flies in early autumn which will attack autumn crops of fruit and fruiting vegetables.
• These flies may spread from urban areas, through peri-urban sites and into commercial crops during this time.
• Action now will cut the next fruit fly generation and increase future home garden and commercial orchard productivity.
  • Essential controls include: fruit and tree removal and destruction, fruit fly baits, netting, monitoring ripening fruit for sting marks or with traps in home gardens, untended areas, council and Crown land, roadsides, riverbanks, business sites, etc.

A total of 9,693 Queensland fruit fly were trapped from about 400 traps so far this fruit fly season (starting from 1 July 2020 to 20 February 2021 compared with 4,774 fruit fly in the previous season (1 July 2019 to 20 February 2020).

The general trend in fruit fly numbers in urban areas is now on the decline as is usual for late summer.

Fruit fly hot spots

The Goulburn Murray Valley regional trapping grid has identified fruit fly pressure across the region and provides essential population tracking data. Current urban fruit fly hot spots include:

The above mentioned sites are of moderate to critical concern for potential hot spot status, so it is important that Goulburn Murray Valley community members with gardens and orchards in these areas take precautions to reduce the ability of fruit fly to infest fruit and to survive in them.

Table 1.

Outlook

Over the next few weeks, the numbers of fruit fly trapped in URBAN LOCATIONS within the Goulburn Murray Valley, are expected to level out in March and then decline a little in April before the major drop-off in May in line with normal trends (see Fig. 1.). It is at this time when it appears that fruit fly migrate from urban areas to commercial orchards in the local district. All members of the community should be on the look-out for fruit fly increases by:

1. Checking monitoring traps
2. Checking ripe or ripening fruit for sting marks and/or larval infestations
3. Cleaning up fallen and unwanted fruit
4. Control activities:
   1. HOME GARDENS: Apply netting to at-risk crops, remove unwanted fruit or whole plants
   2. COMMERCIAL ORCHARDS: Apply netting or fruit fly baits or approved pesticides; remove unwanted fruiting plants; check for Queensland fruit fly in front and back yards of homes, sheds, outhouses, near dams and creeks and orchard perimeter
5. Correct disposal of picked up fruit
6. Letting your neighbours know if there is a fruit fly build-up

Weather forecasts

We are currently in a La Niña weather event that is beneficial to fruit set and maturation, and the development of bacteria, fungi and yeasts which provide feed for adult fruit flies and encourages fruit fly spread and survival. Weather forecasts for March 2021, accessed from the Bureau of Meteorology website http://www.bom.gov.au/climate/outlooks) on 24 February 2021, indicate that there is a 60-70% chance that rainfall over the Goulburn Murray Valley will exceed the average (which is 10-25mm for March based on the past 10 years); there is a 50% chance that maximum temperatures will be higher than the average of 24-30°C and a 75% to over 80% chance that minimum temperatures will be above the average of 12-15°C.

These forecast temperatures are optimal for fruit fly survival and development. Fruit fly survival will be improved with higher than normal minimum temperatures and rainfall will not be limiting. During this period of the year many fruit fly are likely to migrate from home gardens, through peri-urban orchards and gardens and into outlying rural commercial orchards and gardens.

Fig. 2. Rainfall

Fig. 3. Maximum temperature

Fig. 4. Minimum temperature

Goulburn Murray Valley Fruit Fly Project

For assistance in managing Queensland fruit fly, contact the Project Coordinator at the Goulburn Murray Valley Fruit Fly Office by phoning (03) 5871 9222 or emailing 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 by Andrew Jessup, Janren Consulting Pty Ltd in conjunction with the Project Coordinator and analysis of regional trapping data supplied by the GMV Fruit Fly Area Wide Management Project.