Anastrepha fraterculus
(South American fruit fly)

A. fraterculus has a broad host range, particularly in the family Myrtaceae, but it is also a pest of citrus and apples [Malus domestica] in some areas. It is the most important pest species of Anastrepha in subtropical areas of South America, thus it and Anastrepha ludens may be more of a threat of introduction to other subtropical areas of the world than other species of Anastrepha. It is invasive in the Galapagos Islands. As it is probably a complex of cryptic species whose ranges and delimitation remain unresolved, there is also the threat of introduction of particular cryptic species to other areas within the range of the complex. It is considered an A1 quarantine pest by EPPO.

A record of A. fraterculus in Texas, USA (Stone, 1942; EPPO, 2014) published in previous versions of the Compendium is unreliable as the original source of the record (Stone, 1942) is old and was published before the fraterculus group and complex was distinguished (Norrbom et al., 1999). A. fraterculus is considered a quarantine pest in the USA and is regulated at ports of entry (PestID, 2016). USDA-APHIS has an ongoing Mexican fruit fly trapping network in southern Texas, which includes traps capable of attracting A. fraterculus, ensuring that it will be detected if it enters the area (USDA-APHIS-PPQ, 2010, 2015) and triggering response plans, including eradication (USDA-APHIS-PPQ, 2016). There have been no detections of A. fraterculus in the USA in six years of surveys from 2011 to 2016 (NAPIS, 2017).

See also CABI/EPPO (1997).

EPPO lists A. fraterculus as an A1 quarantine pest (OEPP/EPPO, 1983) within the broad category 'non European Trypetidae'; it is also of quarantine significance to APPPC, CPPC and NAPPO. A. fraterculus, like the other Anastrepha spp., derives from tropical wet forest habitats and therefore represents a high risk to similar areas.

Consignments of fruits of Annona, Citrus, Fortunella, Malus, mango [Mangifera indica], peach [Prunus persica] and guava [Psidium guajava] from countries where A. fraterculus occurs should be inspected for symptoms of infestation and those suspected should be cut open in order to look for larvae. For example, EPPO recommends that such fruits should come from an area where A. fraterculus does not occur, or from a place of production found free from the pest by regular inspection for 3 months before harvest. Fruits may also be treated in transit by cold treatment (e.g. 13, 15 or 17 days at 0.5, 1 or 1.5°C, respectively) or, for certain types of fruits, by vapour heat (for example, keeping at 43°C for 4-6 h) (USDA, 1994), or by hot water immersion (Nascimento et al., 1992). Ethylene dibromide was previously widely used as a fumigant, but is now generally withdrawn because of its carcinogenicity. Carneiro and Salles (1994) showed that an entomopathogenic fungus (Paecilomyces fumosoroseus isolate CG 260) could be used to treat larvae entering soil, which then die upon pupariation.

Plants of host species transported with roots from countries where A. fraterculus occurs should be free from soil, or the soil should be treated against puparia, and should not carry fruits. Such plants may be prohibited for importation.

Pest status varies among populations of the fraterculus complex. The populations in Mexico and Central America are less significant pests (e.g. of guava [Psidium guajava], rose apple [Syzygium jambos] and occasionally peach [Prunus persica] and mango [Mangifera indica], but not citrus or apple [Malus domestica]) than some populations in the Andes, southern Brazil, and Argentina that also attack apples, citrus and a variety of other crops (even blackberries [Rubus fruticosus]). Some populations range into subtropical areas in southern Brazil and Argentina and temperate elevations in the Andes, and are pests in those zones.

The complex as a whole is broadly polyphagous (Norrbom, 2004a), but the preferred hosts are Myrtaceae, particularly the native American guava (P. guajava). Other cultivated mytaceous hosts include other Psidium spp., Campomanesia spp., rose apple, Horn of plenty [Feijoa sellowiana], Surinam cherry [Eugenia uniflora] and other Eugenia spp. Prunus spp., especially peach, and loquat [Eriobotrya japonica] are commonly reported hosts. The most frequent introduced hosts in Mexico are S. jambos and Terminalia catappa [Indian-almond] (Hernandez-Ortiz, 1992). Apple, pear, kumquat [Fortunella spp.], peach, loquat and various  Citrus spp. are among the cultivated crops attacked in southern Brazil, although most of the primary hosts are Myrtaceae (Salles, 1995b). Guava, Surinam cherry, grapefruit [Citrus paradisi], cherimoya [Annona cherimola], apricot [Prunus armeniaca], plum [Prunus domestica] and peach are significant hosts in Argentina (Ovruski et al., 2003; Segura et al., 2006).

In common with other polyphagous and difficult to identify species, many host records cannot be substantiated and only records confirmed by Norrbom (2004a) or subsequent reliable sources have been accepted here.

A. fraterculus eggs are laid below the skin of the host fruit. Many Anastrepha spp. lay their eggs deeper inside the fruit or in the seeds. The life cycle includes: the egg, three larval stages, pupa and adult. Salles (2000) presented a table showing the length of development at temperatures from 15-30°C. At 25°C the eggs hatch in 2.6-3.2 days and the larvae feed for another 11-14 days (up to 34.5 days at 15°C). Pupariation is in the soil under the host plant and the adults emerge after 10-15 days (43.2 days at 15°C) and may live up to 161 days in laboratory conditions. Salles (2000) reported that females can produce 278-437 eggs. The adults occur throughout the year (Christenson and Foote, 1960). They have no winter diapause or quiescence in more temperate areas such as southern Brazil (Salles, 1993). Reproductive behaviour in the laboratory and field has been studied by Lima et al. (1994).

No male lures have yet been identified for Anastrepha spp. However, they are captured by traps emitting ammonia. McPhail traps are usually used for the capture of Anastrepha spp. (White and Elson-Harris, 1994) and possible baits are ammonium acetate (Hedstrom and Jimenez, 1988), casein hydrolysate (Sharp, 1987) and torula yeast (Hedstrom and Jiron, 1985). The number of traps required per unit area is high. In a release and recapture test, Calkins et al. (1984) placed 18 traps per 0.4 ha and only recovered approximately 13% of the released flies.

Some studies have shown that egg morphology can be used to separate closely related species found in host fruits (Souza et al., 1983; Murillo and Jiron, 1994). The larvae of some species may also be differentiated using cuticular hydrocarbons (Sutton and Carlson, 1993). Neither method has yet been generalized for application outside of very specific circumstances.

Identification of the fraterculus complex and closely related species is very difficult and is based mainly on measurements and subtle differences in the shape of the aculeus and its tip (Araujo et al., 1996; Araujo and Zucchi, 2006). The species most likely to be confused with A. fraterculus are Anastrepha obliqua, Anastrepha suspensa, and especially Anastrepha sororcula, Anastrepha zenildae and Anastrepha turpiniae.

A. obliqua differs in having the subscutellum entirely orange, not dark-brown laterally. It also lacks the medial spot on the scuto-scutellar suture that is usually present in the fraterculus complex. The aculeus tip is more serrate and less tapered basal to the serrate part. A. suspensa has the apical part of the S-band (the band on the anterior apical margin of the wing) much broader and touching or almost touching the apex of vein M. The other three species are distinguished from the fraterculus complex by the length of the aculeus and its tip, although there is slight overlap in these characters among these species. A. sororcula has a shorter aculeus, with a shorter, stouter tip, whereas A. zenildae and A. turpiniae have longer aculeus tips.

The larvae of Anastrepha are extremely difficult to identify and specialist help should be sought to confirm critical identifications. The third-stage larva is very similar to those of A. obliqua and A. suspensa, and these species usually cannot be distinguished (Steck et al., 1990). The larvae of A. sororcula, A. zenildae and A. turpiniae have not been described.

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.

Control can be considerably aided by good cultural practices, for example, by gathering all fallen and infected host fruits and destroying them. Insecticidal protection is possible by using a cover spray or a 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 in that they can be applied as a spot treatment so that the flies are attracted to the insecticide and there is minimal impact on most natural enemies. However, Nasca et al. (1983) warned that bait sprays could have a substantial effect on Chrysopidae (Neuroptera), which are natural enemies of many pests.

The toxicity to A. fraterculus of different insecticides used in baits was recently compared by Salles (1995) and Lerenzato et al. (1984). They advocated control measures be applied when 0.5-1.0 flies per day per trap were found. Like many fruit flies, shape and colour play a role in host seeking behaviour and Cytrynowicz et al. (1982) found a preference for yellow spheres. The sterile insect technique was tried in Peru (Gonzalez et al., 1971), but has not been applied on a realistic scale.

27/02/2008 Updated by:

Allen Norrbom, Systematic Entomology Laboratory, USDA, c/o National Museum of Natural History, MRC 168, PO Box 37012, Washington, DC 20013-7012, USA