Queensland Fruit Fly Goulburn Murray Valley Outlook June 2019

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.

Fruit fly situation – May 2019

During the first two weeks of May 2019, a total of 368 flies were trapped in the 373 traps deployed in the Goulburn Murray Valley (GMV) giving an average of 0.49 flies per trap per week (FTW). There were 268 flies (0.55 FTW) found in rural trap sites (244 sites) and 98 flies (0.42 FTW) in urban sites (117 sites).Typically trap capture rates are higher in urban areas than in rural areas, however as forecast last month, rural rates are catching up with urban rates as more and more fruit become attractive to Queensland Fruit Fly (QFF) in rural areas. However due to the colder days and particularly the cold nights, rural trapping rates are now decreasing. Urban FTW peak, usually, in late September and then again over an extended period from mid-December to late January. Rural FTW, on the other hand, tend to peak over the period from mid-March to early May.

Figure 1 shows the trends for urban and rural QFF trap captures as flies per trap per week during the entire GMV project duration to date (17 May 2019). Figure 2 shows the same data except that data for rural and urban traps are pooled giving a graph of the total rate of QFF/trap/assessment. The difference between trap capture rates between rural and urban trapping sites is evident throughout most of the project.

The other noticeable trend is the decrease in trapped QFF for the mid-April to mid-May of 2019 (yellow box in Figure 1 and Figure 2) compared with the same period of 2018 (blue box). This difference is most likely to be due to a combination of the effects of the hot, dry summer of 2019 and the community-based area-wide management activities currently underway.

Figure 1. Data from the GMV Fruit Fly Project trapping grid from commencement (May 2017) to present date (17 May 2019) RURAL TRAP RATES VS URBAN TRAP RATES

Figure 2. Data from the GMV Fruit Fly Project trapping grid from commencement (May 2017) to present date (17 May 2019) – QFF TRAPPED PER TRAP PER ASSESSMENT

Queensland Fruit Fly hot spots for May 2019

If your commercial orchard is close to any of the following urban areas which are, at present, registering high QFF populations, you should be ready to commence QFF control programs (if you haven’t already done so):

  • Ardmona
  • Cobram
  • Kyabram
  • Merrigum

It is highly recommended to ensure that your traps are fresh (following label instructions) and placed in suitable locations to intercept QFF coming into your orchard.

Table 1 (on the following page) shows all locations within the GMV where there were significant increases in the numbers of QFF trapped. These sites should be regarded as likely hot spots.

Table 1. Queensland Fruit Fly flare ups occurring within the trapped area of the
Goulburn Murray Valley during the first two weeks of April 2019

Weather outlook

The chance of receiving above average rainfall of more than 25-50mm is not likely (a 35-40% chance for the GMV). Fruit fly would typically find these levels of rain to be limiting but, with irrigation and urban garden watering they may survive, in areas serviced this way, without difficulty.

Maximum temperatures, for the same period, are likely (70-75% chance) to be higher than the average of 12-15˚C. There is a 50% chance that minimum temperatures will be higher than the average of 3-6˚C.

Impact on commercial orchards

Cool overnight temperatures and cooler day temperatures during June will impact adversely on the survival of eggs and larvae that may currently be in fruit and also on pupae in soil. If maximum temperatures are higher than normal for June 2019, as is forecast by the Bureau of Meteorology, dusk temperatures may be at or above 15˚C. If this happens, QFF will mate and then lay eggs and therefore damage the fruit. However, unless infested fruit is in an unusually warm position, it is unlikely that these eggs will mature to live adult flies – but fruit may still be damaged by egg-laying female QFF.

Mean maximum temperatures for the GMV for the week to 20 May 2019 were above

15˚C (Figure 3). This means that it is likely that dusk temperatures in some areas were above 15˚C suggesting it is possible that adult QFF could have laid eggs in unprotected susceptible fruit during this time.

Growers are advised to maintain (or, if not done yet, purchase and place out) their male- and female-targeting fruit fly traps and manually check any ripening fruit in their house yards, orchards or nearby for fruit fly infestations. Growers should also ensure they have timely access to approved fruit fly baits and pesticides should trap numbers and/or fruit infestations increase in severity. Your local Fruit Fly Coordinator, staff from produce stores and Agriculture Victoria can provide advice.

Figure 3. Mean maximum temperatures for Victoria for the week ending 20 May 2019.

Figures 4 to 6 show data extracted from the Bureau of Meteorology outlooks for
May 2019 outlooks for the chance that maximum temperatures, minimum temperatures and rainfall, respectively, will exceed average June weather conditions.

Figure 4. Likelihood that May 2019 maximum temperatures will exceed average June levels (1990 to 2012).

Figure 5. Likelihood that May 2019 minimum temperatures will exceed average June levels (1990 to 2012).

Figure 6. Likelihood that May 2019 rainfall will exceed average June levels (1990 to 2012).

Goulburn Murray Valley Regional Fruit Fly Project

For assistance in managing QFF, contact the 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.