Queensland Fruit Fly Outlook – July 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.

Winter activity – fruit fly situation

It should be remembered that weather conditions vary considerably from area to area and while it may be cold in one area temperatures or rainfall may be higher in another this can vary considerably from location to location depending on the setting. A few degrees higher than average, due to geographical location, may encourage Queensland fruit fly activity even infestation at that site while other cooler areas will not. It is important to keep watch on fruit fly along with the local weather.

From mid-May 2022 to mid-June 2022 about 350 traps were assessed three times. At this time the total numbers of flies trapped in the Goulburn Murray Valley ranged from a weekly high of 692 (the week to 20 May down to the current 82 (the week to 14 June).

Comparison with late autumn 2021 trap captures shows that, for the same four weeks in May-June 2021, the total number of fruit fly caught was 1,483 (from about 360 traps) as opposed to the same period in 2020 with 363 flies trapped (from about 380 traps). It is likely that the observed reduction in Queensland fruit fly numbers trapped, occurring from late autumn 2018 compared with numbers from late autumn 2019 is due to improved management of fruit flies.

Fruit fly survival during mid-May to mid-June was unlikely to have been impacted by weather as conditions have been relatively favourable for fruit flies, at east up to the first week of June.

The percent number of traps that caught zero fruit fly in the first two weeks of May 2022 was 45%. This means that out of 349 traps set up in the Goulburn Murray Valley 55% of them trapped Queensland fruit fly. By mid-June 88.5% of traps trapped 0 flies. This increase is due to the increasing number of cool days as winter approaches when Queensland fruit fly are not attracted to traps. The figure for the same period in 2021 ranged from 48% zero Queensland fruit fly traps to 97%. The difference between the two years is due to extended autumn conditions, favourable to Queensland fly activity, in 2022.

Trapping rates, measuring the numbers of flies trapped per week per trap site (rather than the total numbers of flies trapped over the region) 1 May 2022 to 20 June 2022 in URBAN areas of the Goulburn Murray Valley were higher than those for the same period of 2021 (Table 1). Peri-urban sites were mostly higher in 2022 than 2021 and rural sites were a little lower in 2022 than 2021 except in the first two weeks of June. Higher trap numbers recorded in peri-urban and rural locations than urban areas show that fruit fly is now more active where crop volumes are higher. It is likely that Queensland fly move out of urban sites, through peri-urban locations and then to rural areas due to the attraction of high volumes of ripening and ripe fruit. The extended autumn weather conditions during 2022 contributed to an extension of positive fruit fly activity during the first two weeks of June.

Table 1. Queensland fruit fly trapped per trap per week in the Goulburn Murray Valley based on land use type

Urban and peri-urban areas

Tasks to undertake in urban and peri-urban areas include:

• Destruction of unwanted fruit
  • Destroy fruit by sealing in plastic bag (leave in the sun for 5 days and then throw out with the weekly garbage or compost), freezing, microwaving, burning, cooking, drying, immersion in water, break open and feed to animals, etc.
  • Eat the removed fruit either fresh, preserved or cooked.
  • Rake out fallen fruit in orchards into the open and mash or mulch.
  • Completely remove the fruiting plant and replace with an ornamental one.
  • Pick up and dispose of any fallen fruit that may be in your yard, on the nature strip, on nearby creek banks or parks.
  • Pick any fruit still on the plant and either use or dispose of as above.
• Prune your trees to keep them at a manageable height for next season’s fruit picking or for netting.
• Check ripe and ripening fruit for signs of fruit fly infestation – soft patches, brown to black sting marks, maggots. If found, pick the fruit and dispose of it as above.
• If you have traps out – whether they are male-targeting or female-targeting, make sure that they are within the use-by date. If not, put new ones out or recharge them with new baits.
• If you don’t have traps out consider putting a few around the house, especially in evergreen foliage near the house, chook yard or the compost heap – e.g. the lemon tree.
• Netting around most trees can be removed now but keep it there if you have ripe or ripening fruit still in your yard. Remember that olives can be attacked by fruit flies when they are black and ripe.
• If you have fruit trees that you don’t use – e.g. feijoa, guava – consider removing them completely and replacing them with an attractive non-fruiting plant.

Rural areas

If your property is close to (within 500m) of the hot spot areas mentioned below or near untended host plants, or feral hosts along roads, channels or in abandoned orchards you should keep a very close watch on:

• Fruit fly traps (both male and female targeting) are most useful when deployed in

and around susceptible orchards all year round. If not, then July would be the best

time to start trapping.

✓ Check your traps at least once a week

• Any ripe or ripening fruit (in your orchard, in your house yard, including the front yard, or along the road or channel bank) that might show signs of infestation (e.g. sting marks, abnormal fruit softening).

✓ Check your fruit (for sting marks and/or eggs and larvae inside them at least once a week

• If you have had fruit fly problems previously it is advisable to ensure you have access to suitable quantities of fruit fly bait so that if fruit flies are found in fruit or in high numbers on traps you can commence your baiting program straight away
• Ensure your orders for fruit fly baits and, if necessary, fruit fly cover sprays, have been sent into your supplier

It is highly recommended to ensure your traps are fresh (following label instructions) and placed in suitable locations to intercept Qfly coming into your orchard. It is also highly recommended to commence, if not already done, a bait-application program. This is especially important if you or your neighbours experienced fruit fly problems last season.

Fruit fly hot spots

Even though temperatures are falling in the Goulburn Murray Valley over the winter months there are still a few locations where significant fruit fly populations are persisting. It’s possible that these areas have very high populations as some sites which are warmer than other areas. In these cases, fruit fly move from fruiting plants to shelter plants where they can safely survive winter away from the cold and predators.

Weather outlook and impact on fruit fly

Data from the Bureau of Meteorology forecast that chances of rainfall for the July 2022 are above the average of 25-100mm are likely (a 60 to 70% chance for the Goulburn Murray Valley). These levels of rainfall encourage fruit fly survival.

The likelihood of maximum temperatures, for the same period, to be higher than the average of 12-15˚C vary from an even chance (50 to 55%) in the north-west of the Goulburn Murray Valley to likely (65 to 70%) in the south-east of the Goulburn Murray Valley. These temperatures are not limiting to fruit fly survival although they are generally too low for mating and fruit infestation.

On the other hand, there is a likely chance (65 to 75%) that minimum temperatures will be higher than the average of 3-6˚C. These temperatures are also favourable to fruit fly survival during the winter as long as the adults can find refuge from wind and cold. There will be minimal mating and fruit infestation and the ability of fruit flies to fly from tree to tree will be inhibited.

The abovementioned forecast weather conditions point to the probability that fruit fly will survive the Goulburn Murray Valley winter in greater numbers than in previous colder, drier years. It is very important to make sure all fruit and fruiting vegetables are harvested and used or picked up and destroyed. Remove all fruiting plants whose fruit are never used.

Goulburn Murray Valley Fruit Fly Program

For assistance in managing Queensland fruit fly, 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.