Bactrocera xanthodes
(Pacific fruit fly)

Pictures

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Identity

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Preferred Scientific Name

• Bactrocera xanthodes (Broun)

Preferred Common Name

• Pacific fruit fly

Other Scientific Names

• Chaetodacus xanthodes (Broun)
• Dacus xanthodes (Broun)
• Notodacus xanthodes (Broun)
• Tephritis xanthodes Broun

EPPO code

• BCTRXA (Bactrocera xanthodes)

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Diptera
•                         Family: Tephritidae
•                             Genus: Bactrocera
•                                 Species: Bactrocera xanthodes

Notes on Taxonomy and Nomenclature

Top of page B. xanthodes belongs to subgenus Notodacus and its name may therefore be cited as Bactrocera (Notodacus) xanthodes (Broun).

Description

Top of page Adult

The genus Bactrocera belongs to the family Tephritidae, which is part of the superfamily Tephritoidea. In common with most species of Tephritoidea it has patterned wings, and the female has a long telescopic and pointed ovipositor; these features are rarely known outside the Tephritoidea. The family Tephritidae may also be separated from all other Diptera by the shape of the subcostal vein, which bends abruptly through a right-angle and fades to a fold before reaching the wing edge, combined with the presence of setulae along the dorsal side of vein R1. At the wing base, species of Bactrocera and Dacus have a very deep cell bm and a very long pointed extension of cell bcu (= cup). The genus Bactrocera is separated from Dacus by the terga (dorsal sclerites of the abdomen) not being fused into a single sclerotized plate.

B. xanthodes belongs to subgenus Notodacus, an unusual feature of which is the presence of a seta on each postpronotal lobe (i.e. shoulder). It has a very distinct V-shaped notch in the apex of its scutellum. B. paraxanthodes has this to a lesser extent (and so presumably do the two undescribed species) but this feature is at most very weakly developed in other members of the genus. Another unusual feature of B. xanthodes is that the lateral stripes (vittae) on the scutum extend forward to the postpronotal lobes and back down the sides of the scutellum. There is also a third (medial) yellow stripe that extends to the posterior edge of the scutum (immediately before the scutellum); this stripe is shorter in B. paraxanthodes

Larva

A full description was provided by White and Elson-Harris (1994). Many species in the Pacific area remain unknown in their larval stages but this species is probably unusual in having a pigmented transverse line between the intermediate lobes on abdominal segment 8.

Distribution

Top of page Heimoana et al. (1997) noted that records from Niue still require confirmation. The distribution was mapped by Drew (1982) but at that time it was not known that some undescribed species were being misidentified as B. xanthodes. Subsequently, Drew and Hancock (1995) have described B. paraxanthodes from New Caledonia. There are also known to be two undescribed species awaiting formal description, one from Vanuatu (Allwood et al., 1997) and another from Samoa (Heimoana et al., 1997).

B. xanthodes may have been spread between some islands by man and it has been suggested that the species only reached the Cook Islands in the early 1970s (Purea et al., 1997).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

Top of page B. xanthodes poses a phytosanitary risk to other countries with a suitable tropical climate and suitable hosts crops, particularly breadfruit.

Hosts/Species Affected

Top of page In Fiji, populations of B. xanthodes are linked to fruiting times of the major wild hosts, namely Ochrosia oppositifolia (Apocynaceae) and Barringtonia edulis (Lecythidaceae) (Tora Vueti et al., 1997b). However, Tora Vueti et al. (1997a) suggested that small islands with abundant breadfruit (Artocarpus altilis) provided a suitable location for this species. Drew et al. (1997) notes that B. xanthodes has 19 commercial hosts and 9 recorded wild hosts, although many of those records remain unpublished. Drew et al. (1997) also noted that a record from pineapple (Ananas comosus) derived from 1905 data that has never been replicated. More seriously, they questioned a record from watermelon (Citrullus lanatus) as it was only based on a single find of larvae (not substantiated by any adult specimens) from an over-ripe fruit intercepted from Tonga in New Zealand. However, that interception resulted in the development of post-harvest technology for this species (Stechmann et al., 1988; Cowley et al., 1991) and a complete ban on the import of watermelons into New Zealand from the Pacific Islands (Anon., 1986).

Hamacek (1997) noted that more research is needed to separate the host records of B. xanthodes from those of three related and previously confused species.

Host Plants and Other Plants Affected

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Growth Stages

Top of page Fruiting stage

Symptoms

Top of page Attacked fruit usually shows signs of oviposition punctures around which necrosis may occur.

List of Symptoms/Signs

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Biology and Ecology

Top of page Little is known about the life cycle of B. xanthodes under field conditions. Mature female Bactrocera oviposit into fruit, usually at the start of ripening (may vary with fly or host species); there are three larval instars and they develop over a period of ca 1-4 weeks; final instar larvae of Bactrocera drop to the ground, find a crack to drop into, and then form a puparium (hardened larvae skin) within which pupation takes place; adults may be expected to emerge after 1-4 weeks; adults of known species of Bactrocera are long lived (1-3 months) and so several generations must be completed in each year. In the laboratory, Clare (1997) found that at 26°C the larvae developed in 10 days and the total cycle (egg to egg) was 35 days.

Natural enemies

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Notes on Natural Enemies

Top of page Waterhouse (1993) summarizes knowledge of fruit flies (species of Bactrocera), their natural enemies and biological control in the Pacific region. There are remarkably few records of parasites from B. xanthodes. Biological control introductions have been made into countries where B. xanthodes is present, but few parasites became established in any of them and no satisfactory control has been obtained.

Means of Movement and Dispersal

Top of page Adult flight and the transport of infested fruits are the major means of movement and dispersal to previously uninfested areas.

Pathway Vectors

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Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Leaves
Roots
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches
True seeds (inc. grain)
Wood

Impact

Top of page Although B. xanthodes attacks a number of commercial fruits in several South Pacific islands, there is little documentary evidence that it is really a serious pest. Most collected individuals have been trapped and probably derived from its two major wild hosts.

Detection and Inspection

Top of page Males are attracted to traps baited with methyl eugenol. Both sexes may be monitored using protein bait traps (either protein hydrolysate or protein autolysate) but these traps also collect large numbers of non-target insects; see Drew (1982) for further details.

Similarities to Other Species/Conditions

Top of page The most obvious difference between the closely related B. paraxanthodes and B. xanthodes is that B. xanthodes has yellow lateral margins to the scutellum while B. paraxanthodes has dark margins. For other differences, and notes on two undescribed species of subgenus Notodacus, see Drew et al. (1997).

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

When detected, it is important to gather all fallen and infected host fruits, and destroy them. Baited traps should be used to monitor population size and spread continuously. Insecticide protection is possible by using a cover or bait spray. Malathion is the usual choice of insecticide for fruit fly control and this is usually combined with protein hydrolysate to form a bait spray (Roessler, 1989); practical details are given by Bateman (1982). Bait sprays work on the principle that both male and female tephritids are strongly attracted to a protein source from which ammonia emanates. Bait sprays have the advantage over cover sprays that they can be applied as a spot treatment so that the flies are attracted to the insecticide and there is minimal impact on natural enemies.

References

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Allwood AJ, Tumukon T, Tau D, Kassim A, 1997. Fruit fly fauna in Vanuatu. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:77-80.

Allwood AJ, Vueti ET, Leblanc L, Bull R, 2003. Eradication of introduced Bactrocera species (Diptera: Tephritidae) in Nauru using male annihilation and protein bait application techniques. In: Turning the tide: the eradication of invasive species: Proceedings of the International Conference on eradication of island invasives [ed. by Veitch, C. R.\Clout, M. N.]. Gland, Switzerland: IUCN-The World Conservation Union, 19-25.

Bateman MA, 1982. III. Chemical methods for suppression or eradication of fruit fly populations, In: Drew RAI, Hooper GHS, Bateman MA eds. Economic Fruit Flies of the South Pacific Region. 2nd edn. Brisbane, Australia: Queensland Department of Primary Industries, 115-128.

Clare GK, 1997. Rearing of Bactrocera melanotus and B. xanthodes (Diptera: Tephritidae) for postharvest disinfestation research. New Zealand Journal of Zoology, 24(2):193-198; 28 ref.

Cowley JM, Baker RT, Englberger KG, Langi TG, 1991. Methyl bromide fumigation of Tongan watermelons against Bactrocera xanthodes (Diptera: Tephritidae) and analysis of quarantine security. Journal of Economic Entomology, 84(6):1763-1767

Drew RAI, 1982. Fruit fly collecting. In: Drew RAI, Hooper GHS, Bateman MA, eds. Economic Fruit Flies of the South Pacific Region, 2nd edition. Brisbane, Australia: Queensland Department of Primary Industries, 129-139.

Drew RAI, Allwood AJ, Tau D, 1997. Bactrocera paraxanthodes Drew and Hancock - an example of how host records and attractant responses contribute to taxonomic research. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:131-133.

Drew RAI, Hancock DL, 1995. New species, subgenus and records of Bactrocera Macquart from the South Pacific (Diptera: Tephritidae: Dacinae). Journal of the Australian Entomological Society, 34(1):7-11

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Hamacek E, 1997. Host records of fruit flies in the South Pacific, In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:102-104.

Heimoana V, Tunupop F, Toleafoa E, Fakanaiki C, 1997. The fruit fly fauna of Tonga, Western Samoa, American Samoa and Niue. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:57-59.

IPPC, 2015. Pest outbreak on Niulakita Island. IPPC Official Pest Report, No. TUV-02/4. Rome, Italy: FAO. https://www.ippc.int/

New Zealand, Ministry of Agriculture and Fisheries, 1986. Quarantine. Report of the Ministry of Agriculture and Fisheries for the year ended 31 March 1986 Wellington, New Zealand; Government Printer, 26-27

Purea M, Putoa R, Munro E, 1997. Fauna of fruit flies in the Cook Islands and French Polynesia. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:54-56.

Roessler Y, 1989. Control; insecticides; insecticidal bait and cover sprays. In: Robinson AS, Hooper G, eds. Fruit Flies. Their Biology, Natural Enemies and Control. World Crop Pests 3(B). Amsterdam, Netherlands: Elsevier, 329-336.

Stechmann DH, Englberger K, Langi TF, 1988. Estimation of mortality of Dacus xanthodes (Broun) maggots in fumigated and non-fumigated watermelons, a fruitfly (Dipt.: Tephritidae) of plant quarantine importance in the Pacific Region. Anzeiger fur Schadlingskunde, Pflanzenschutz, Umweltschutz, 61(7):125-129

Tora Vueti E, Allwood AJ, Leweniqila L, Ralulu L, Balawakula A, Malau A, Sales F, Peleti K, 1997. Fruit fly fauna in Fiji, Tuvalu, Wallis and Futuna, Tokelau and Nauru. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:60-63.

Tora Vueti E, Ralulu L, Walker GP, Allwood AJ, Leweniqila L, Balawakula A, 1997. Host availability - its impact on seasonal abundance of fruit flies. In: Allwood AJ, Drew RAI, eds. Management of Fruit Flies in the Pacific. A Regional Symposium, Nadi, Fiji. ACIAR Proceedings, 76:105-110.

Waterhouse DF, 1993. Biological control: Pacific prospects - supplement 2. Canberra, Australia: ACIAR, 138 pp.

White IM, Elson-Harris MM, 1994. Fruit Flies of Economic Significance. Their Identification and Bionomics. Wallingford, UK: CAB International.

Distribution Maps

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