Queensland Fruit Fly Outlook – February 2020

Queensland Fruit Fly Goulburn Murray Valley Outlook February 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.

Current trends in Queensland Fruit Fly populations and February 2020 outlook

Key points:

• Trapping data indicates the usual spring peak in Queensland Fruit Fly (QFF) numbers occurred in the Goulburn Murray Valley (GMV).
• Currently 88 per cent of the region’s QFF population is located in urban sites.
• Weather conditions are currently suitable for fruit fly to mate and lay eggs although hot, dry weather in some areas, will reduce the numbers of fruit available for QFF to sting. The heat will kill eggs and larvae in fruit that is exposed to the sun.
• If you have fruit in your orchard or garden that is not wanted – for example fruit fallen on the ground, unharvested fruit still in the tree or fruit you never pick and eat, pick up and destroy this fruit. If fruit will ripen off-tree it should be picked and allowed to ripen, alternatively if you can harvest fruit early or cook fruit green, you should do so.

A total of 3,197 QFF have been trapped from 394 traps so far this fruit fly season

(commencing mid-August 2019). Rural traps caught 384 flies (12%) during this period, while the majority (2,795 flies or 88%) were trapped in urban locations.

The general trend in QFF numbers is now on the rise, as is usual for the period from late December to February. Last year’s fruit fly season saw a depression in the normal rise in numbers from December 2018 to February 2019. In comparing this data to the previous seven years, it is observed that a combination of Area Wide Management and periodic weather conditions that adversely impact QFF survival kept numbers down. A similar pattern is occurring this season.

The current population increase is occurring predominantly in urban areas of the GMV.
However, February 2020 will see the start of the annual rise in numbers in rural locations. In Figure 1 below actual trapping data (QFF/trap) and the associated trend in trapping results are shown. The blue trend line indicates that, if the same patterns as February 2019 emerge, it is expected trapping numbers will commence their annual increase in February 2020 – meaning that commercial crops ripening and being harvested at that time or soon after are at risk of infestation. The two arrows show that trapping rates were higher in February 2019 than so far in 2020. It’s likely that weather events, in addition to Area Wide Management strategies that growers may have implemented, has resulted in this decrease.

Figure 1. Trends in rural trapping data for QFF in the GMV. See text above for explanation of blue and red arrow.

Queensland Fruit Fly hot spots

At present most potential QFF hot spots are located in the urban areas of:

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

Rural hot spot

There is one rural spot situated near Cobram where QFF populations have been increasing relatively rapidly.

Outlook

Over the next few weeks the numbers of QFF trapped in the GMV, will rise rapidly in urban areas and more slowly in rural areas, if typical patterns are followed. This will be the commencement of the peak fruit fly season for 2019/20, which will then spread from urban areas to commercial orchards in the local district.

Currently, and for the remainder of February, there is little chance of QFF spreading to commercial orchards unless early fruit is to be found, (possibly in domestic gardens near the house or sheds). It is highly recommended to be particularly vigilant for fruit fly invasions in orchards within 5km of the potential hot spot sites mentioned above as there is a risk of QFF moving in and damaging fruit ripening in late summer and autumn.

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

Weather forecasts for February 2020, accessed from the Bureau of Meteorology website (http://www.bom.gov.au/climate/outlooks) on 23 January 2020, indicate that there is a 50% chance that rainfall over the GMV will exceed the average (which is 25-50mm for February); there is a 75% chance that maximum temperatures will be higher than the average of 2733°C and a 75% chance that minimum temperatures will be above the average of 12-18°C.

While forecast temperatures are optimal for fruit fly survival, predicated rainfall is a limiting factor as 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.

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.