QFF numbers tend to increase in spring, when temperatures become warmer and suitable host plants, such as apricots, apples, berries, tomatoes and capsicums, become available.

The times given here for each phase of the QFF lifecycle can vary, depending on temperature and other conditions. From the age of about two weeks, adult QFF females can mate (typically at dusk) and deposit about seven eggs through a fruit puncture or “sting” into a fruit. A single female QFF may deposit up to 100 eggs per day. Females often oviposit into punctures made by other fruit flies, which can result in many eggs occurring in a single cavity of a fruit.

About three days after laying, QFF eggs hatch into larvae or maggots which eat toward the centre of the fruit, causing it to rot. After two to four weeks, maggots grow to their full size of about 9 mm in length, by which time the fruit often has fallen to the ground.

The maggot then chews its way out of the remaining fruit into the soil and enters the pupal stage of development. Depending on temperature, this stage lasts between one and four weeks. These then hatch from the soil as mature adult flies, typically near the end of the summer season.

Unlike other fly pests, QFF do not breed continuously, but overwinter in their adult stage and can live for many months. Up to four or five overlapping generations may occur annually. Adult flies are reliant upon leaf surface bacteria as their major source of protein.

What measures are used to reduce the impact of QFF?

In commercial orchards, QFF was commonly controlled by the application of the pesticide chemicals dimethoate and fenthion until about ten years ago, when they were suspended from use because of safety concerns. As a result, modern QFF reduction or elimination methods have been developed, based on studies of this pest’s behaviour. Farmers in affected regions are encouraged to use lures such as pheromones, food attractants, host mimics, or colour attractants. Recommended killing mechanisms often involves pesticides, liquid traps in which the pest drowns, or sticky traps from which the pest cannot escape.

Additional control measures include using fine netting to protect individual fruit or entire trees. Traps and lures for killing or monitoring purposes are commercially available.

How can I reduce the impact of QFF on my own garden and neighbourhood?

The control methods described above are quite time- and energy-intensive. So if QFF is an issue in your area, you’ll probably want to find ways to deal with it with minimal effort. Things to try include:

• Reduce the number of fruiting plants in your garden

• Try growing fruits which ripen early in the season, when QFF numbers tend to be lower

• Plant dwarf fruit varieties and learn to prune them to keep them small, to make them easy to inspect, net and harvest

• Set commercial or homemade QFF traps or lures. A range of suitable commercial products are available. You can also try making homemade male QFF traps – recipes for these using protein and sugar baits abound online, but note that these require frequent refreshing to be effective.

• Collect fallen fruit immediately, before larvae can emerge and burrow, and deal with it as described above

• Be circumspect about sharing fruit and vegetables with neighbours and friends

• Avoid transporting harvested fruit to other areas

• Pay attention to which varieties of fruit are more or less QFF resilient, and plan accordingly. For example, some apple and tomato varieties clearly vary in their susceptibility

• Run chickens under susceptible fruit trees so they can clean up fallen fruit and consume larvae and emerging QFF adults

• Discuss QFF control and the responsible handling of affected fruit with your friends and neighbours, especially if they are growing susceptible plants

What is the Heritage Fruits Society doing regarding QFF?

Some (but not all) varieties of the apples in the HFS heritage collection at Petty’s have been attacked by QFF this year. This suggests that some varieties are more resistant than others, knowledge we can usewhen we advise the public of which apple varieties they should grow. 

We expect the situation to improve in the HFS collection as new QFF control methods being adopted for all of Petty’s Orchard take effect. In the meantime, we’re carefully monitoring all fruit we pick. We’re also ensuring that everyone who accesses our fruit is aware that it’s potentially QFF-affected, and informing them of what to do if it is (see photo of our information card, below).

In the meantime, the Society is aiming to help inform as many people as possible about the challenges QFF pose to fruit growers and others, and measures they can take to sensibly and effectively deal with this dreadful pest.