25/02/2025
Summary 📣
As of 14 February 2025, Qfly populations have levelled off after building up during the first half of January 2025.
While the heat will have killed some eggs and larvae inside infested fruit, many will survive if the fruit falls into the shade of weeds, grass and canopies of host plants. Also, most adult Qfly will have found refuge from the heat and dryness in broadleaved evergreen trees or may have migrated to gardens and orchards.
Weather forecasts for March 2025 point to upcoming favourable conditions for Qfly survival and population build up with higher than normal maximum and minimum temperatures and possibly slightly more rainfall than usual. Home garden, public garden and orchard irrigation will improve Qfly survival and build up, especially now that commercial crops are beginning to ripen in the GMV. The majority of GMV’s fruit crops are highly favourable hosts to Qfly.
Now is the time to ensure all unwanted fruiting plants, or their fruit, are culled from home gardens, front yards, around sheds, along creek banks, nature strips, abandoned or untended fruiting plants and Government land. Continued active management is necessary to avoid population build up in late summer and autumn 2025.
Location Effect 🏡
Average Qfly numbers/trap/week are currently higher in some locations than others. This is reflected by the volume and type of Qfly host plants in each location as well as the level of fruit fly management being employed there.
Some sites, such as Merrigum and Lemnos, have just started Qfly build-up while others, such as Invergordon, Kialla East and Mooroopna, have declined in Qfly numbers. These changes are due to changing fruit maturities. Other sites, such as Kyabram and Shepparton appear to be more persistent hot spots probably due to the presence of a much larger mixture of plants fruiting at different times during the season.
Land use type 🗻
Peri-urban trap sites are showing an increasing trend in Qfly numbers while numbers in urban traps declined during the second week of February. This could be due to the majority of fruits having been harvested or eaten by birds in urban sites thus promoting the migration of Qfly into peri-urban areas. Despite a jump in early February in rural locations, Qfly numbers are still low but fruit crops there are now beginning to ripen and these will become a powerful attractant for Qfly to move from urban and peri-urban areas into commercial cropping areas.
Individual rural sites which have high Qfly numbers at this time are likely to have persistent Qfly populations surviving in untended home gardens and untended non-commercial fruit trees on the block.
As urban crops decline with harvest, hot, dry weather and bird predation in the summer the numbers of Qfly found in traps also decrease while peri-urban and rural increase. This reflects the movement of Qfly from urban, through peri-urban and into rural areas from mid-summer to autumn. This occurs due to the “pull” of large volumes of commercial crops ripening in rural areas at this time.
Weather ⛅️
Current weather trends compared with previous years:
Current rainfall accumulation is low and this will have an impact on both fruit set and Qfly reproduction and survival. This benefit, however, will be moderated by irrigation.
Temperature trends over the past four seasons show maximum temperatures being significantly higher than previous years – and for a prolonged period up to 14 February 2025. This situation, especially with the low rainfall is likely to be unfavourable to Qfly except under irrigation.
Long-range weather forecast overview
Issued: 13 February 2025 (http://www.bom.gov.au/climate/outlooks/ #/overview/summary/ - accessed 17 February 2025).
The long-range forecast for March indicates:
• warmer than average days are likely to very likely across most of Australia, with an increased chance of unusually high daytime temperatures across much of the country
• warmer than average nights are very likely across Australia, with an increased chance of unusually high overnight temperatures nationwide.
Rainfall 🌨
The Bureau of Meteorology (BOM) predicts (http://www.bom.gov.au/climate/outlooks - accessed 17 February 2025, Fig. 8) a 55% to 60% chance of more rainfall than the average for the GMV (10mm to 50mm for March) meaning that March rainfall should be close to, or slightly above, average. This condition is marginally favourable to Qfly survival and proliferation although irrigation will offset any disadvantage.
Maximum temperature ☀
Predicted maximum daily temperatures in the GMV are highly likely (65% to 75% chance, Fig. 9) to be warmer than usual (27°C to 33°C for March in the GMV). These conditions are mostly favourable to Qfly survival and population build up, especially if under irrigation. If temperatures reach much above 34°C exposed Qfly eggs, larvae and adults may perish. However, eggs and larvae in fruit on the ground (in the shade) will survive and adults will move to cool, shady and moist locations in dense broadleaved evergreen plants until the weather becomes more suitable.
Minimum temperature ☁️
Predicted minimum daily temperatures in the GMV are very highly likely (greater than 85% chance, Fig. 10) to be warmer than usual (9°C to 15°C for March in the GMV). These conditions are favourable to Qfly survival and population build up especially when daytime temperatures are above 15°C which is the case in much of the GMV during March.
Forecast 🐛
The Qfly forecast is that Qfly populations will increase in the GMV from early summer into autumn. At this time Qfly will move from urban areas, through peri-urban sites and into neighbouring rural locations. This build up can be slowed down or even eliminated with sound and effective area wide management strategies that commence early in the season and are maintained throughout the year.
