Queensland Fruit Fly Outlook – March 2020

Queensland Fruit Fly Goulburn Murray Valley Outlook March 2020

This information has been commissioned by the Goulburn Murray Valley (GMV) Regional 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.

Information for commercial growers

Key points:

• Trapping data reveals the GMV has passed this fruit fly season’s peak in urban-based fruit fly captures BUT Queensland Fruit Fly (QFF) captures are on the rise in rural locations of the GMV.
• Currently 22% of the GMV’s fruit fly population is located in urban sites (up from 12% in January 2020).
• As daily temperatures start to get cooler, conditions become ideal for QFF to mate and lay eggs.
• Eggs laid during February will become a new generation of pest fruit flies in early autumn and attack autumn fruit and fruiting vegetables crops.
• Even if you have protected your orchards from fruit flies in the past these flies may spread from urban areas, through peri-urban sites and into orchards during this time.
• Action now will cut the next QFF generation and increase future home garden productivity. Action to undertake includes:
  • Fruit and/or tree removal and destruction, making sure you monitor your fruit fly traps for surges in QFF numbers, check ripe and ripening fruit for signs of infestation (sting marks, presence of eggs and/or larvae, premature fruit drop and fruit softening/rotting), apply weekly fruit fly baits 6 weeks before harvest (especially if you had problems last season).
  • Check nearby untended areas with fruit trees such as Council and Crown land, roadsides, riverbanks, business sites, etc.
  • Don’t forget to check fruiting plants in gardens in your front yard, house yard and areas around sheds and outhouses.
• Releases of sterile QFF in the urban area of the Cobram township, under the SITplus Pilot Project, along with the region’s area-wide management program continue to show very promising results in reducing QFF populations.

Trapping data

A total of 4,781 QFF were trapped from about 400 traps so far this fruit fly season (starting from mid-August 2019). Rural traps caught 1,046 QFF (22%) during this period while the majority (3,735 or 78%) were trapped in urban locations.

The general trend in QFF numbers in rural areas is now on the increase as is usual for early autumn (see Table1). If the trend identified over the past three years continues this season, March 2020 will see the start of the annual rise in QFF numbers in rural locations.

Data in Table 1 reveals that, on average, in RURAL locations, QFF numbers actually increase in March and April each year. Peak QFF trappings, in URBAN areas occurred some months earlier (December and January). During February and March it appears that QFF migrate from urban areas to nearby rural locations.

Queensland Fruit Fly hotspots

Potential QFF hotspots have been identified in the following urban areas:

These sites are of moderate to critical concern for potential hotspot status and community members with gardens and orchards in these areas should take precautions to reduce the ability of QFF to infest fruit and to survive in them.

Rural hotspot

There are now two rural locations where QFF populations have been building up relatively quickly near Cobram and Merrigum.

SITplus Pilot Project – Cobram

The SITplus (Sterile Insect Technique) project continues to release sterile QFF over Cobram as part of a pilot program. The project aims to eventually wipe out wild QFF populations and continues to show high control levels as measured by numbers of QFF in traps in the urban area of Cobram. It is hoped that this decline will translate to a reduction in QFF numbers in nearby peri-urban and rural locations.

Autumn outlook

If QFF populations follow normal trends, the number of fruit fly trapped and recorded in the GMV will begin to level out in urban areas in coming weeks and rise rapidly in rural areas. This activity will mark the commencement of the peak fruit fly season for commercial orchards within the region for the 2019/2020 harvest season.
Commercial growers should be on the look-out for increased QFF activity 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. Controlling QFF by apply netting (if commercially viable or to protect home garden plants) use of fruit fly baits or approved pesticides, removing unwanted fruiting plants and checking for QFF in front and back yards of homes, sheds, outhouses, near dams and creeks and orchard perimeters;
5. Correct disposal of unwanted fruit;
6. Letting your neighbours know if you experience a QFF build-up.

Over March, QFF will commence spreading to commercial orchards via early ripening fruit in peri-urban and rural areas (possibly in domestic gardens near the house or sheds or in unattended crops, creek and dams banks, roadsides and Council and Crown land). It is highly recommended to be particularly vigilant for fruit fly invasions in orchards within 5km of the potential hot spot sites mentioned above. They may be at risk from QFF moving in and damaging fruit ripening in autumn.

Fruiting weeds such as blackberries are good hosts for QFF so it is wise to reduce these fruit so that they do not act as a reservoir for future QFF problems.

Weather forecasts

Weather forecasts for March 2020, accessed from the Bureau of Meteorology website (www.bom.gov.au/climate/outlooks) on 20 February 2020, indicate that there is a 55% to 65% chance that rainfall over the GMV will exceed the average (which is 10mm to 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°C to 30°C and a 65% to 70% chance that minimum temperatures will be above average of 9°C to 15°C.

Although these forecast temperatures are optimal for QFF survival and development, rainfall is a limiting factor. Even if there is more rain than average it is still lower than optimal for QFF. However, in home gardens where weather conditions are modified by irrigation, and the presence of evergreen plants for refuge and early fruits and vegetables for egg-laying, QFF will thrive if not managed correctly. During this period of the year many QFF will likely migrate from home gardens, through peri-urban orchards and gardens and into outlying rural commercial orchards and gardens.

Goulburn Murray Valley Regional Fruit Fly Project

For assistance in managing QFF, contact the Project Coordinator at GMV Fruit Fly Office by phoning (03) 5871 9222 or emailing gmvfruitfly@moira.vic.gov.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 Project.