Fruit
Fly Trapping for Quarantine Surveillance
in The Pacific Islands Countries and Territories
The use of traps baited with a chemical lure that attract male flies is the easiest way to maintain quarantine surveillance. Of the various male lures available, two are most commonly used for trapping in PICTs: methyl eugenol and Cue-lure. Methyl eugenol may attract flies from a distance of up to 500 metres. Cue-lure's range of attractiveness is much less than that of ME - up to 300 metres. Many species are not attracted to Cue-lure or ME and can only be adequately sampled through host fruit surveying. These include several economically important species such as B. atrisetosa, B. decipiens and B. obliqua. Major pests to be kept outside the PICT region and that do not respond to male lures include cucumber fruit fly (Bactrocera cucumis (French)), a pest of cucurbits, tomato and papaya in Australia, and solanum fruit fly (B. latifrons (Hendel)) a pest of tomato, eggplant, capsicum and chilli in Asia and Hawaii.
Of the numerous male lure trap models, the modified Steiner trap is used throughout the Pacific. It is a horizontal plastic cylinder with an opening at each end; one end is removable. Cotton dental wicks treated with the lure solution are suspended inside the trap. The solution is a mixture of 4 parts lure to 1 part Malathion (50% emulsifiable concentrate). Flies, attracted to the lure, enter the trap through the openings at the ends, feed on or come in contact with the lure and are killed by the insecticide. The trap is attached to a tree branch within the canopy, two metres above the ground, with a wire that must be coated with a non-drying adhesive, such as Tanglefoot, that prevents ants, other insects, spiders and lizards from entering the trap and eating the flies.
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| Modified Steiner trap for fruit fly surveillance (Photo: L. Leblanc) |
Two traps (one Cue-lure and one ME) are usually set at each trapping site. Trapping sites may be located at agriculture stations, commercial plantations, villages, towns and primary forests. For quarantine surveillance against unwanted exotic species, traps should be placed in suburban areas, tourist resorts, refuse dumps, near diplomatic missions, at education institutes that cater to overseas students, and ports of entry, to detect foreign species that may be introduced through contaminated exotic fruits brought in by travelers.
Only one lure must be used per trap. To avoid cross contamination of lures, two operators are required for trap clearance, one responsible for handling and emptying the contents of traps with Cue lure and the other person responsible for servicing the ME trap. Traps are emptied weekly in easily accessible sites, otherwise every two weeks or monthly for sites that are a far away. The lure mixture in the cotton wick is renewed every three months, using a dropper.
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| Trap servicing (Photos A.C. Clarke - left, and A.J. Allwood - right) | |
Trapped flies from one sample are placed inside a small cardboard box with strips of tissue paper to prevent flies from moving and getting damaged during transport and storage. Each box must be accurately labeled with trap number, type of lure (Cue or ME), location, date of emptying and collector’s name. Samples must be kept in a dry place that cannot be reached by ants. A few grains of thymol should be added to each specimen box to prevent build-up of mould on specimens.
Page updated on: 17 October, 2002