Understanding the life cycle of the fruit fly can tell you a lot about how these pests can best be controlled and how different control methods can be integrated. Without an understanding of the life cycle of fruit fly, you may end up using control methods in a way that fail to solve your pest problem.
Having a basic understanding of the life cycle of fruit fly can help you determine:
- how a particular life stage affects your crop
- when the pest is likely to be present, and of the greatest threat to your garden
- when the pest is most susceptible to control and for how long
- how a particular life stage is affected by a control method
- how you can create unfavourable conditions for the pest in your garden
- when it is too late to control.
Stages of the life cycle
There are four stages to the life cycle of fruit flies, these are: eggs, larvae (maggots), pupae and adults. A brief description of each of the stages of the life cycle of fruit fly is provided below.
The female adult fly lays eggs (1-20) into the maturing and ripening fruit of the host plant. The eggs hatch into larvae inside the fruit after a few days (2-4 days). Note that at this stage of the life cycle you are unlikely to be able to recognise the presence of fruit fly eggs in your fruit as the eggs are very small. During its lifetime, a female fruit fly may lay 400 eggs or more.
The hatching larvae (maggots) feed inside the fruit and are accompanied by various bacteria that are introduced when the female fly lays its eggs. The activity of the maggots and the bacteria causes the fruit to rot internally and often affected fruit will prematurely fall from the free. The larval stage is the most likely stage that you would recognise the presence of fruit fly in your fruit if you cut it open.
As the fruit ripens and rots, it falls to the ground. Fully mature larvae leave the fruit and burrow into the soil to pupate. In the soil, larvae become inactive and change into oval shaped, light to dark brown, hard pupae. Inside the pupal case, which is the cocoon or chrysalis formed by butterflies, the adult fly develops. At this stage you are unlikely to recognise the presence of fruit fly pupae in the ground.
The adult flies may emerge from the pupae in as little as seven days during the summer, or after several months over winter. The adult fly looks for the nourishment it needs to reach maturity, breed, and lay eggs in new season crops. At this stage of the life cycle you may be able to recognise adult flies landing on or sheltering amongst vegetation or landing on fruit.
Behaviour of fruit flies
Fruit fly numbers tend to increase, usually in spring, when temperatures are warm and there is continued availability of suitable host plants. Under good conditions, fruit flies develop from eggs to adults within four to five weeks.
Characteristics of adult flies:
- Take about a week from emergence to reach sexual maturity.
- Rest in shady trees (fruit trees, ornamental trees and shrubs) during the day.
- Feed on bacteria that can be present on the host tree or adjacent plants.
- Queensland fruit flies mate at dusk, while Mediterranean fruit flies mate at any time of the day.
- Can survive throughout winter.
Characteristics of female fruit flies:
- Sting fruit and vegetables from October to May (though some activity will occur in warmer periods during the winter months).
- Lay eggs into healthy, maturing and ripening fruit (on the tree) and vegetables.
- Need to feed on a source of protein before eggs will mature for laying.
- Reabsorb eggs during extended periods of cold weather.
Video: Queensland fruit fly in your garden
Agriculture Victoria developed the following video about about the life cycle of Queensland fruit fly, how it spreads, and how to monitor fruit and vegetables for signs of infestation and control numbers.