Bactrocera latifrons
(Solanum fruit fly)

The distribution map includes records based on specimens of B. latifrons from the collection in the Natural History Museum (London, UK): dates of collection are noted in the Table (NHM, London, UK).

B. latifrons has a predominantly south and south-east Asian distribution. Waterhouse (1993) records this species from Indonesia, although no area is specified. Given that this species has been found in Sabah and West Malaysia it may at least be expected in Kalimantan and Sumatra.

In Africa, B. latifrons has only been recorded from Tanzania and Kenya. Its occurance in other parts of Africa is currently unknown (Meyer et al., 2007).

This species was recently introduced to Hawaii and was first discovered there in 1983 (Liquido et al., 1994).

A distribution map has been produced by IIE (1996).

The major risk is from the import of fruit containing larvae, either as part of cargo, or through the smuggling of fruit in airline passenger baggage or mail. For example, in New Zealand Baker and Cowley (1991) recorded 7-33 interceptions of fruit flies per year in cargo and 10-28 per year in passenger baggage. Private individuals who successfully smuggle fruit are likely to discard it when they discover that it is rotten. Larvae have been found in peppers sent by mail from Hawaii to California (Foote et al., 1993).

B. latifons is a pest of solanaceous crops. Recent studies in Hawaii confirmed that B. latifrons can also develop in a few species of Cucurbitaceae, but it was out-numbered by B. cucurbitae in these hosts, which were cucumber (Cucumis sativus), ivy gourd (Coccinia grandis), wax gourd (Benincasa hispida) and white-flowered gourd (Lagenaria siceraria). The recent surveys carried out by Allwood et al. (1999) showed that other families can be attacked but only rarely, e.g. guava (Psidium guajava), pomegranate (Punica granatum) and citrus (Citrus aurantifolia).

Eggs (9-587 eggs) are laid below the skin of the host fruit. These hatch within a few days (mean 2.3) and the larvae feed for about a week (mean 8.5 days). Pupariation is in the soil under the host plant for little over a week (mean 10.2 days). Adults occur throughout the year and females begin oviposition after 6-17 days, and continue laying eggs for 6-117 days; data from Vargas and Nishida (1985). Adult flight and the transport of infected fruit are the major means of movement and dispersal of Bactrocera spp. to previously uninfected areas. A pre-adult life-table for B. latifrons was produced by Vargas and Nishida (1985) and further ecological studies were carried out by Liquido et al. (1994) who showed that B. latifrons outcompeted B. dorsalis, B. cucurbitae and Ceratitis capitata in its Solanaceous hosts but not in its non-Solanaceous hosts. For further information on the biology and ecology of B. latifrons, see Sunil Kumar and Agarwal (2003), Peck and McQuate (2004) and Ishida et al. (2005).

[Erratum: In previous versions of this datasheet, it was stated that “many Bactrocera spp. can fly 50-100 km (Fletcher, 1989)” but a review of Fletcher (1989a) and Fletcher (1989b) by Hicks et al. (2019) found no evidence to support this statement and it has been removed. Fletcher (1989b) provides dispersal data for only 11 of 651 species of Bactrocera, many of the case studies lack the necessary numerical data, and the study did not discern between active flight and passive wind-assisted dispersal. There are differences among fruit fly species and further studies are required to determine dispersal distances for individual species. For further information on trapping Bactrocera species to monitor movement, see Weldon et al. (2014).]

Bactrocera spp. in general can be attacked as larvae either by parasitoids or by vertebrates eating fruit (either on the tree or as fallen fruit). Mortality due to vertebrate fruit consumption can be very high as can puparial mortality in the soil, either due to predation or environmental mortality (see White and Elson-Harris, 1994, for brief review). Parasitoids appear to have little effect on the populations of most fruit flies and Fletcher (1987) noted that 0-30% levels of parasitism are typical. However, Diachasmimorpha kraussii is being tested for its specificity as a potential biocontrol agent in Hawaii (Duan and Messing, 2000). Bokonon-Ganta et al. (2007) studied the parasitoid complex naturally established against B. latifrons in Hawaii with the aim of assessing the need to improve the biological control of this species. The main parasitoids were Fopius arisanus, Psyttalia incisi, Diachasmimorpha longicaudata, D. tryoni and Tetrastichus giffardianus. Levels of parasitism were low suggesting the need to improve control by augmentative releases of the predominant parasitoid, F. arisanus, or introduction and release of specific and efficient parasitoid species. To date complete biological control, in the classical sense, has never been achieved for any Bactrocera or Dacus spp. (Wharton, 1989). Nonetheless, biological control programmes can result in significant reduction in pest populations. Such reductions have led to relatively pest-free cultivation of at least some less susceptible varieties of fruits and vegetables. Liquido et al. (1994) did produce a full list of recorded parasitoids and discussed the low levels of parasitism of B. latifrons. However, due to difficulties in verifying identifications that list is not reproduced in full here. The short list of natural enemies is taken chiefly from Wharton and Gilstrap (1983) and Waterhouse (1993).

Fruits (locally grown or samples of fruit imports) should be inspected for puncture marks and any associated necrosis. Suspect fruits should be cut open and checked for larvae. Larval identification is difficult, so if time allows, mature larvae should be transferred to saw dust (or similar dry medium) to allow pupariation. The use of cuticular hydrocarbons for larval identification has been investigated (Sutton et al., 1996) but in most circumstances many more species will need to be compared before this can be applied. Upon emergence, adult flies must be fed with sugar and water for several days to allow hardening and full colour to develop, before they can be identified.

Adult B. latifrons have a yellow strip on the side of the thorax and a mostly red-brown abdomen. Females have a pair of preapical ‘shoulders’ on the aculeus (Meyer et al., 2007). For further information see Invasive Fruit Fly Pests in Africa (Meyer et al., 2007).

B. latifrons was one of six Bactrocera species identified by a PCR-DGGE method based on the gene analysis of mtDNA CO II and 16S rDNA (Zhan et al., 2007). The method was shown to be a rapid and specific technique for identifying pest species in plant quarantine.

Of the species likely to be reared from cultivated Solanaceae, it is one of only two whose anepisternal stripe comes close to contacting the postpronotal lobe (the other being B. facialis from Tonga); and of those two, it is the only species that both has its costal band expanded into a spot at the wing apex, and has a dark spot in each antennal furrow. Given a female specimen whose aculeus apex happens to be exposed (with a freshly dead specimen it can be exposed by gently squeezing the oviscape with watch-makers forceps), then the trilobed apex can be seen with a high powered stereo microscope. No other species likely to be reared from cultivated Solanaceae has both a point and pre-apical "steps" in its aculeus apex. Wing length 4.4-6.1 mm.

Minimum characters to differentiate from most other Bactrocera and Dacus spp. (White and Hancock, 1997): Face with a dark spot in each antennal furrow. Scutum predominantly black; with lateral vittae; without medial vitta; with prescutellar acrostichal setae. Scutellum entirely yellow (except for narrow basal line). Anepisternal stripe almost reaching postpronotal (=humeral) lobe. Cell bc colourless. Costal band expanded into a spot at apex. Tergite 4 without any lateral markings. Aculeus apex trilobed.

B. latifrons was included in a pictorial key to Sri Lankan species (also largely applicable to southern India) by Tsuruta (1998).

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.

Regulatory Control

Many countries, such as the mainland USA, forbid the import of susceptible fruit without strict post-harvest treatment having been applied by the exporter. This may involve fumigation, heat treatment (hot vapour or hot water), cold treatments, insecticidal dipping, or irradiation (Armstrong and Couey, 1989). However, recent research has indicated that B. latifrons is more heat tolerant than other species (Jang et al., 1999). Irradiation is not accepted in most countries and many have now banned methyl bromide fumigation. Heat treatment tends to reduce the shelf life of most fruits and so the most effective method of regulatory control is to preferentially restrict imports of a given fruit to areas free of fruit fly attack.

Cultural Control and Sanitary Methods

One of the most effective control techniques against fruit flies in general is to wrap fruit, either in newspaper, a paper bag, or in the case of long/thin fruits, a polythene sleeve. This is a simple physical barrier to oviposition but it has to be applied well before the fruit is attacked. Little information is available on the attack time for most fruits but few Bactrocera spp. attack prior to ripening.

Chemical Control

Although cover sprays of entire crops are sometimes used, the use of bait sprays is both more economical and more environmentally acceptable. A bait spray consists of a suitable insecticide (e.g. malathion) mixed with a protein bait. Both males and females of fruit flies are attracted to protein sources emanating ammonia, and so insecticides can be applied to just a few spots in an orchard and the flies will be attracted to these spots. The protein most widely used is hydrolysed protein, but some supplies of this are acid hydrolysed and so highly phytotoxic. Smith and Nannan (1988) have developed a system using autolysed protein. In Malaysia this has been developed into a very effective commercial product derived from brewery waste.

Field Monitoring

This species is not attracted to either cue lure or methyl eugenol. Field monitoring is by sampling susceptible fruits for larvae. In Hawaii a new lure chemical is being developed (see White and Liquido, 1995).