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Fruit Fly (using organic methods)

What do they look like?
The Queensland fruit fly is native to Australia and occurs throughout Queensland and NSW. It is reddish-brown with yellow markings, slightly larger than a housefly. Ripening fruit is its favoured target, so fruit that is picked green is usually not affected. The adult female lays her eggs under the skin of the fruit in clumps of 6-12.

What do they do?
Eggs take 1-2 days to hatch into white maggots in ripening fruit.. These maggots feed in the fruit for 7-12 days and then drop to the ground and pupate. The pupae are 5mm long, elongated and brown. The adult fruit fly emerges from the pupae after 10-14 days. The whole life cycle takes 4 weeks under ideal environmental conditions. Cool dry conditions can cause the life cycle to be extended past 4 weeks. Most fruit and vegetables are susceptible to fruit fly when fruit begins to ripen.

Can we live with them?
No

How are they controlled?
Exclusion bags made of calico or brown paper will give protection (mailorder available from www.greenharvest.com.au). Spraying with insecticides can be dangerous and is not normally necessary until about 6 weeks prior to ripening. The insecticide label should be strictly adhered to and withholding periods followed.

We have had success with using an organic product called Econatralure. However the way you use it is essential- some gardeners have not used it correctly and have been disappointed. Read the details below for more information.

Using econaturalure:

The main thing is that the product must be applied early in the season, from August.

It is the female fruit fly that lays eggs in fruit, so the female is the one to target. Female fruit flies have a peculiar life cycle in that once they emerge from the ground they need to feed on a protein source in order to become sexually mature. After this initial feeding stage they may not feed again - they may be too busy mating and laying eggs. So it’s best if you can get the fruit fly while they are still in their juvenile feeding stage. Later applications of eco-naturalure may still attract the adult female fruit fly but they may have already stung the fruit. Early application will help reduce the total population of fruit flies which will mean less damaged fruit.

By early December you will probably have dormant fruit fly already in the fruit. Fruit fly can lay their eggs into rock hard fruit, and we know that in Strathfield in western Sydney, for example, fruit fly were active by late winter. You need to apply the spray as soon as the flowers on your stone fruit drop; or the flowers of a loquat or any other early fruiting plant in your area drop.

Remember too that fruit fly must feed on the product, so if it is painted on and it dries out, runs off or is absorbed by the material it is painted onto, then it will not be effective. Painting the product on with a brush may also leave product stuck in the bristles, so application via a spray set to a non-mist setting is best. The product must be applied so that the droplets of eco-naturalure are available for the fruit fly to suck up - preferably from the branches and foliage or a lamb fleece placed close to fruit at mid-canopy height. Fruit fly are shy, and may not venture into exposed areas away from plant foliage.

Please also note application rates for boards and foliage differ. Board application is 10ml eco-naturalure to 15ml water, while foliar application is 10ml eco-naturalure to 60ml water. Each mixture should be applied to one square metre area of board or foliage-and-branches per fifty square metre area that requires protection. Weekly applications are most effective, and eco-naturalure should be reapplied after rain.

The number of fruit fly in an area will make it hard for some residents to get the results they want. Where insect pressure is high it will take more than one person using the product to reduce fruit fly numbers. eco-naturalure is no "silver bullet"! But over time and with increased use we can diminish populations, and provide gardeners with cleaner fruit.

Technical notes about eco-naturalure are available to all members of the Garden Clinic Club. Just call 1800 634 204 and the notes can be posted or emailed to you.