Exotic fruit flies like the Queensland and Mediterranean fruit fly are among the most serious pests of fruit tree gardeners in warmer regions everywhere. These pests burrow into the soil. The brown pupal cases are about 5 mm long and look like somewhat elongated hens’ eggs. They become active around the end of winter, when the weather begins to warm. The flies lay their eggs in small groups just beneath the skin of the fruit. When the larvae hatch, they generally make their way to the centre of the fruit.
Plant Part: Fruit
Season: End of Spring - Summer
Symptoms: You will see brown holes in the skin of your fruit, sometimes surrounded with rotten areas of the fruit but not always. These holes can cause the area around the hole to “sink in”. The insect then burrows toward the centre of the fruit. Note: Fruit fly damage can also look similar to Codling Moth damage. Fruit can be cut open to determine which pest has infiltrated your fruit. Codling moth only infect apples and have a large larvae inside whereas fruit fly larvae look smaller, more like maggots.
Control: There are 2 methods available to control fruit fly. You can either exclude fruit fly by netting your tree and preventing the fruit fly from reaching your fruit, or you can control the fruit fly by the use of traps or spraying your trees.
The most effective way to control fruit fly is insect or fruit fly proof netting covering your tree. This netting prevents fruit fly from getting to the fruit. Netting can be draped over your tree or supported by a frame.
Make sure the netting is installed AFTER pollination has occurred as bees need access to the flowers to pollinate them so they produce fruit. Nets can be purchased at most nursery and garden centres, and are the easiest way to ensure your fruit crop is protected.
You can also control fruit fly through the use of baited fruit fly traps or spraying your tree. There are a range of fruit fly baiting and trapping options available, and while these are not difficult to use, they require consistent effort throughout the growing season and need to be installed before the fruit starts to ripen. See your local garden centre for trapping and baiting options. Biotrap offers a range of fruit fly management options including short and long term traps, and fruit fly netting. Visit their website here.
Spraying can kill eggs and larvae in the fruit. If choosing to use a chemical spray, avoid sprays with Fenthion (particularly toxic to birds).
Prevention: Good garden hygiene is critical to controlling these pests. Always remove infested and fallen fruit from your garden. Fruit inside the netting is protected but you dont want to be breeding fruit fly in the fallen fruit right under your trees.
As above, the most effective way to prevent fruit flies damaging your produce is to use fruit fly or insect proof netting. Such netting can be bought from some specialist garden centres and online retailers. Insect proof netting can be draped over trees and other crops or supported by a frame. Netting needs to be put up after pollination has occurred.
References: QLD Department of Agriculture, Fisheries and Forestry, WA Department of Agriculture & Food, Sustainable Gardening Australia , Biotrap, Prevent Fruitfly.com.au and our FST team.
