Photo 1. Queensland fruit fly, Bactrocera tryoni. Note, the yellow stripe towards the edge of the thorax as seen from above.
Queensland fruit fly; abbreviation QFF.
Restricted. Oceania. It is recorded from Australia (New South Wales, Northern Territory, Queensland, and Victoria), French Polynesia, New Caledonia, and Pitcairn.
Over 200 fruits and vegetables are hosts in 49 flowering families. Some of the main hosts are Annona species (soursop, custard apple, sugar apple), apple, avocado, capsicum, carambola, cashew, Citrus species, coffee, eggplant, guava, Indian almond (Terminalia catappa), Malay apple, mango, Pacific lychee (Pometia pinnata), papaya, passionfruit, peach, rose apple, sapodila, sapote, Surinam cherry, Tahitian chestnut (Inocarpus fagifer) and tomato. Wild hosts are fish poison tree (Barringtonia asiatica), Java nut (Canarium vulgare), noni, and Phyllanthus (leafflower) species. Pineapples are not a host.
The QFF is a severe pest of a wide range of fruits and vegetables, capable of existing in diverse climates. It is potentially invasive as it infests fruit often carried by people while travelling.
Eggs are white, 1 mm long, banana-shaped, laid inside ripe fruits and vegetables just below the surface. The QFF can lay up to 100 eggs a day in small batches of 6 or so. Often, several females lay in the same fruit. The eggs hatch in 2-4 days and when mature the maggots are 7 mm long, carrot-shaped with an ability to curl into a 'U'-shape and jump. They chew their way out of the host and fall to the ground, burrowing into the soil to pupate.
Adults are 5-8 mm long (female longer than the male), brown marked with yellow, with transparent wings, 10-12 mm across (Photos 1&2). They use bacteria on leaf surfaces as a major source of protein (the basis of control measures using protein-bait sprays). There may be four to five overlapping generations a year. Activity increases after rains or during high humidity. Spread of QFF occurs on the wing, they are strong fliers, and as larvae in infested fruit.
Waterhouse1 states: "The Queensland fruit is the most destructive pest of fruit and vegetables in tropical, sub-tropical and temperate eastern Australia. It infests... all commercial crops except pineapple". Losses to fruit flies in Australia if not controlled is put at A$100 million a year, mostly due to QFF.
Look for the red-brown colour of the thorax from above, with its two yellow stripes towards the sides (Photo 1). Look for the small black spots on the face below the antennae. Male flies are attracted to Cue-lure (a sex pheromone) and both males and females to protein baits. Traps containing either of these ingredients are usually hung within shade tree canopies, one or two per ha (Photo 3).
Countries not yet infested by the QFF should consider all likely pathways for entry, and apply quarantine measures accordingly. Fruit and vegetables may need to be treated to manage risk of fruit fly introduction by, e.g., high-temperature forced-air, low temperature, insecticide dips, irradiation, area freedom, or area-wide management..
The invasiveness of the fruit is shown by introductions to New Caledonia (1969), French Polynesia (1970) that have not been eradicated, and introductions into Western Australia (1988), Easter Islands (1971) and Cook Islands (2005) that were eradicated. Recent outbreaks (2019) in New Zealand, as well as in fruit-fly free areas of South Australia, Victoria and New South Wales are under eradication.
Although parasitism can be up to 30% it is not thought to affect levels of damage. Fopius arisanus, Diachasmimorpha tryoni and Diachasmimorpha karaussii are the parasiotoids considered to have potential as biocontrol agents.
AREA FREEDOM FROM FRUIT FLY
Many countries have government schemes to check for fruit fly incursions and to comply with market access protocols. This is the basis of control in commercial areas, such as the Greater Sunraysia Pest Free Area in parts of Victoria and NSW, Australia. The aim is to prevent any fruit fly invading the area from completing its life cycle. It is supported by a number of cultural control measures.
Traps are placed at sea and airports and in fruit-fly free areas on a 1 km grid format (possibly less in urban areas, and around orchards), and checked weekly. Control programs are triggered based on the number and sex of flies caught per trap within a specified time interval. Public awareness, preventing uncontrolled fruit and vegetables entering the designated fruit-fly free areas, is central to the success of the strategy.
AWM is used to reduce populations of fruit flies by monitoring, trapping with pheromone, protein bait sprays, male annihilation technique, cover sprays and the implementation of cultural practices within a local area by getting growers and the community to collaborate throughout the year. An example is the Yarra Valley QFF Action Plan, Victoria, Australia.
This is usually attempted by i) defining a 1.5 km quarantine area around the outbreak site, ii) control of fruit movement, iii) removal of fruit on infested trees and collecting fallen fruit, iv) protein bait and insecticide sprays (to attract and kill male and female flies), v) management of green waste, and vi) male annihilation technology (high density traps, 10-20 per ha, containing sex pheromone plus insecticide in compressed fibreboard or cardboard). Sterile insect technology (SIT) is frequently applied after protein bait sprays with the release of 100,000 sterile flies per km2 twice a week for up to 12 weeks.
The control measures that follow are especially for home gardens or smallholdings, although the same principals and methods are applicable to larger commercial enterprises.
Grow fruits and vegetables that are non-hosts of Queensland fruit fly. However, only a few are listed by Agriculture Victoria: choka, coffee berries, date, dragon fruit. Pineapple is a non-host, mentioned above.
Cover sprays over the entire crop have given way to protein bait sprays as they are more economical. Previously, dimethoate and fenthion were used widely. In Australia, fenthion is no longer permitted, but dimethoate is still registered. Conditions of dimethoate use against QFF depend on the crop and (in some crops the variety), how grown (field or protected cropping), the use of the crop (fresh consumption or processing), when and how applied (dip or spray) and concentration; therefore, see manufacturers' instructions for details. In general, dimethoate is used on fruits with inedible peel. Dimethoate is not allowed for home garden use in Australia. Use of dimethoate in the European Union will expire in July 2020.
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.
AUTHOR Grahame Jackson
Information (and Photos 1&2) Hinkley S, Walker K (2005) Queensland Fruit Fly (Bactrocera tryoni). PaDIL - http://www.padil.gov.au; and Ekman J (2016) Fruit fly management for vegetable growers. Applied Horticulture Reseach. Horticulture Innovation Australia. (http://ahr.com.au/wp-content/uploads/2017/01/Fruit-Fly-guide-Booklet.pdf); and Information for gardeners. Agriculture Victoria. (http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/pest-insects-and-mites/queensland-fruit-fly/gardeners); and CABI Bactrocera tryoni (Queensland fruit fly) (2018) Crop Protection Compendium. (http://www.cabi.org/cpc); and from Waterhouse DF (1993)1 Biological Control Pacific Prospects - Supplement 2. ACIAR Monograph No. 20. Brown Prior Anderson, Burwood, Victoria.
Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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