Rising pressure

Fruit fly populations are in the middle of the spring peak. These flies are overwintering adults that have left their winter refuges in search of mates and fruit to infest. Many of these adults have already mated and laid eggs.

The next generation of fruit fly will emerge from eggs laid by overwintering flies that were able to survive winter. The size of this population will impact on subsequent damage caused to crops in urban and rural areas of the Goulburn Murray Valley from late December 2021 onwards. Fruit fly numbers will steadily increase in late December and continue this increase throughout January to April, with a small decline during January when very hot, dry weather occurs.

Fruit fly hot spots

Current hot spot locations requiring extra vigilance include:

  • Kyabram
  • Orrvale
  • Mooroopna
  • Shepparton

Weather impact

Weather analysis for September/ October 2021 show that some areas of the region are more susceptible to post-winter proliferation than others. For example, Cobram, Yarroweyah and Strathmerton had 12 days where sunset temperatures were over 15˚C (the time and minimum temperature at which fruit fly mate) while Mangalore and Avenel had only 6 days. November trapping numbers may be higher in areas where sunset temperatures were over 15˚C early in spring and are unlikely to peak until later in the season in areas that did not experience these temperatures.

The Bureau of Meteorology predicts there is a high chance that above average rain will fall during November 2021, while maximum temperatures are forecast to remain similar to the average. The chances that minimum temperatures will be higher than average are high. These conditions are favourable for fruit fly survival and population build-up.

Advice for commercial orchardists

Growers should have traps placed out in the orchard and areas around the house and sheds. If your orchard is close to hot spot areas (mentioned above) ensure you check traps regularly and check crops and other fruiting plants in and around your orchard – house paddocks, front yard, roadsides and along water-courses. Baiting is efficient at controlling fruit fly so ensure you have stocks in storage within the use-by date, especially if fruit fly was present in your area last year.