Weather conditions ideal for fruit fly
Queensland Fruit Fly (Qfly) populations vary throughout the year. They also vary from year to year based on the impacts of the weather and area-wide fruit fly management strategies.
The most recent spring peak is higher than that of previous years due to weather conditions during autumn and early winter of 2020 providing ideal conditions for fruit flies to survive the winter.
During this time there was more rain than average, which pushed up minimum daily temperatures leading into winter. This allowed more fruit flies than usual to emerge from late-infested fruit and find refuge before cold winter temperatures began.
The optimum weather situation for Qfly survival through spring and into summer is for November to receive above-average rainfall and above- average maximum and minimum temperatures.
This situation occurred in the winter of 2016, which resulted in extremely high spring, summer and autumn Qfly populations across the central and northern parts of Victoria. It looks like this situation will occur again in 2020/21.
Warmer than normal minimum temperatures, plus extra rainfall, will see more fruit and therefore more fruit flies in the Goulburn Murray Valley this coming season. If home gardeners and growers can manage fruit flies adequately this trend will be reversed.
Advice to commercial growers
If control measures are not in place Qfly populations, aided by higher than normal rainfall and minimum temperatures, will increase from November 2020. November is the time to continue checking fruit for sting marks, setting traps for monitoring purposes and ensuring you have adequate Qfly control material (traps, baits and pesticides) in stock and on-hand. It is also recommended to check that any pesticides in storage are within their use-by dates and still approved for use in your state and your fruit type.
Don’t forget to check your house garden, as Qfly may have survived the winter by finding refuge in evergreen plants in warm spots near the house or packing/machinery shed. If neglected, this habitat may give Qfly an early start in your orchard.