Copyright © 2014 Albury Wodonga Fight the Fruit Fly Association Inc.
Queensland fruit fly (QFF) is one of the world’s worst pests of fruit and fruiting vegetables.
In urban areas, it poses a serious threat to the enjoyment of home-grown fruits and vegetables because the feeding activity of QFF maggots makes produce inedible.
Its presence can also add to the cost of delivering produce to wholesale markets, which may ultimately result in higher retail prices.
In fruit production areas, QFF damage has the potential to cost Australian fruit growers more than $100 million each year. Victoria’s horticulture industries are particularly vulnerable to this pest.
Home gardeners in all areas have a vital role to play in controlling QFF and preventing it from spreading. By caring for your fruit trees, disposing of fruit properly and reporting suspected detections of QFF, you can protect your home-grown produce and help reduce the economic impact of this pest.
What should I look for?
You should regularly inspect your home-grown fruit for QFF larvae (or maggots), which are more likely to be detected than adult flies.
Fruit will normally need to be cut open to check for maggots, because infested fruit may appear to be in good condition from the outside. See photo gallery>
The maggots are 5-10mm long and creamy-white in colour. Adult QFF are about 7 mm long and reddish brown in colour, with distinct yellow oval markings. Female flies lay eggs in ripening fruit and the maggots which hatch from the eggs burrow into the fruit and destroy it.
There are more than 100 fruits which are hosts of fruit fly, including:
Peach, nectarine, grapefruit, pear, avocado, grape, cumquat, apricot, orange, fig, quince, tomato, eggplant, passionfruit, plum, lemon, apple, loquat, chili, capsicum and strawberry.
For a comprehensive list go to the DEPI website by clicking here>
What can I do?
If you have QFF host plants in your garden, you should:
Prune your fruit trees regularly, keeping the tops at a height which will make fruit picking easy. Remove any ripe fruit from host plants before it has a chance to fall to the ground.
Collect any fallen fruit immediately and place it in a plastic bag. Seal the bag of fruit and either leave it in the sun for 5-7 days or place it in a freezer for two days. This will destroy the maggots and prevent adult flies from developing. The bagged fruit can then be discarded in your garbage bin.
Compost carefully - do not place unwanted fruit in your compost or worm farm, or put it directly into your garbage. Remove any unwanted fruit trees from your property.
Unlike several of the other most important fruit fly pests, B. tryoni does not breed continuously but passes the winter in the adult stage. The total life cycle requires two to three weeks in summer and up to two months in the fall. Adult females live many months, and four or five overlapping generations may develop annually. Adult females, after passing through a two-week pre-oviposition stage following emergence from the pupae, deposit eggs in groups, up to seven eggs per group, in fruit punctures. Females often oviposit in punctures made by other fruit flies such as those of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), with the result that many eggs often occur in a single cavity. As many as 40 larvae have been found in one peach, and as many as 67 adults have been reared from one apple. Eggs hatch in two to three days under favorable weather conditions. The ensuing larval development may be completed in as little as five days. Pupation normally occurs in the soil. Pupal development requires from a week in summer to a month or more in cooler weather. Adults may live a year or more. Adults feed primarily upon juices of host plants, nectar, and honeydew secreted by various kinds of insects
Immature stages are similar in appearance to those of other Bactrocera. The adult female is approximately 6 mm long, has a wing expanse of 10 to 12 mm, and has mostly transparent wings marked with brown. The fly is brown marked with yellow. On the thorax a broad creamy, often pale, dorsal band runs down the scutellum, and there is a well-defined narrow pale yellow stripe on each side. The humeri, or shoulders, are pale yellow, also. The abdomen is constricted at the base, flared in the middle, and broadly rounded at the tip, not counting the ovipositor of the female.
The Queensland fruit fly is native to Australia and occurs throughout Queensland. It is reddish-brown with yellow markings, slightly larger than a housefly and has wasp-like features. Ripening fruit are its favoured target, so fruit that are picked green-mature may not be affected. However when green fruit are stung a hard callused tissue may form around the eggs, preventing larval development. Damage symptoms include a puncture mark that may be difficult to see, gum exudation, localised ripening around the sting and premature fruit drop.
Once the adult female has mated, she then lays her eggs under the skin of the fruit using her ovipositor. The white, 1 mm long, spindle shaped eggs are laid in clumps of 6-12 and take 1-2 days to hatch in ripening fruit. The eggs hatch into white maggots which reach 9 mm long. These maggots live and feed in the fruit for 7-12 days and then drop to the ground and pupate. The pupae are 5 mm 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 only susceptible to fruit fly once the fruit begins to mature and ripen, as a result spraying is not normally necessary until about 6 weeks prior to ripening. The insecticide label should be strictly adhered to and withholding periods followed.
Bait sprays contain an autolysed protein and insecticide. The bait is sprayed onto the lower leaves of fruit trees according to label directions. The autolysed protein is highly attractive to both the male and female Queensland fruit fly, and as the fruit fly feeds on the protein bait it also ingests the insecticide killing it. Bait sprays effectively control fruit fly on citrus, avocado and passionfruit. They may not provide adequate control when fruit fly numbers are high. Some fruit trees may require cover sprays for successful fruit fly control. Bait spray products available to home gardeners include 'Fruit fly lure' which contains the insecticide maldison and 'Naturalure fruit fly bait' which contains the biologically produced insecticide spinosad.
Home made traps can be made by putting several 6 mm diameter holes in the neck of a 1 litre plastic bottle, placing a bait in the bottle to attract the fruit fly and an insecticide such as 'Malathion' to kill the fruit fly. The trap is hung in a shady part of the tree just above the lower leaves. The fruit fly is attracted to the smell of the bait, enters the bottle, feeds on the bait and is poisoned at the same time. The bait should be replaced in the trap twice a week to keep it fresh and attractive to the fruit fly. The trap should be hung in the fruit tree at least six weeks prior to anticipated picking and until all of the fruit has been picked, as this is when fruit is most attractive to the fruit fly. This type of treatment may not provide adequate control when fruit fly numbers are high.
Ripe fruit should not be left on or lying under the fruit tree, as this is an ideal breeding ground for the fruit fly. Spoilt fruit should be disposed of by immersing in water, boiling or burying to a depth greater than 50 cm
Individual fruit or fruit clusters can be bagged with cloth or waxed paper bags. More information>
Queensland fruit fly pheromone trap
Unlike bait sprays and the home-made traps, this trap only attracts the male Queensland fruit fly. The trap consists of a pheromone treated wick combined with an insecticide and is held in a plastic container with holes in it large enough for the fruit fly to enter. It is hung in the lower branches of the host tree and is used to monitor fruit fly presence and reduce the male Queensland fruit fly population in the local area.
Note – All pesticides listed in this note were current at the time of publication. Pesticides should be applied strictly according to label direction.
The Lifecycle of Queensland fruit fly
As with most insects, there are four stages in the life cycle: eggs, maggots, pupa and the adult fly.