Exotic fruit flies like then Queensland and Mediterranean fruit fly are among the most serious pests of fruit tree gardeners in warmer regions everywhere. Adult Queensland Fruit Flies are about seven millimetres long and are reddish-brown in colour, with distinct yellow markings.
Plant Part: Fruit
Season: End of Winter - Summer
Symptoms: 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.
Control: Infested fruit must be removed from the ground or from the tree and destroyed by burning or boiling. Maggots will also be killed if the fruit is sealed in a plastic bag and left in the sun for several days. It must NOT be buried as this simply continues the normal life cycle of the insect. Traps will only kill the adult fly but used in conjunction with sprays is generally effective – you need to remove all infected fruit straight away. If the infestation is extreme, then consider using a mixture of systems to control the fruit flies; fruit fly traps set up with Lures and MAT cups work in conjunction to kill the flies.
Spraying can kill eggs and larvae in the fruit. If choosing to use a chemical spray avoid sprays with Fenthion (particularly toxic to birds). Previously, suitable fruit fly baits were a mixture of Maldison and protein (lure) but you need to be careful using Maldison as it is harmful to bees. Naturalure™ fruit fly Bait concentrate is a good all in one product to try. Apply per the manufacturer instructions.
Prevention: Good garden hygiene is critical to controlling these pests. 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.
Bugs for Bugs have some great fruit fly traps and sprays that might help.
If you live in an area that is known for fruit fly then look at choosing our early cropping varieties that can be harvested before Christmas when fruit fly numbers are lower.
Reference: QLD Department of Agriculture, Fisheries & Forestry, Department of Agriculture & Food, Western Australia, Agriculture Victoria, Bugs for Bugs and of course our FST team.
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