Bactrocera invadens a new invasive species of fruit fly: addition to the EPPO Alert List
In March 2003, during routine field surveys in the Coast Province of Kenya, a new fruit fly species suspected to belong to the Bactrocera dorsalis group (originating from Asia) was detected (EPPO RS 2004/100). 2 specimens were caught in protein-baited traps and 1 was reared from an unidentified fruit (probably a Strychnos sp.). Considering the potential risk presented by this type of fruit fly, further surveys were immediately initiated across the major fruit-growing and trading localities in Kenya using methyl-eugenol and Cue Lure traps. Traps (120 with methyl-eugenol and 15 with Cue Lure) were placed in mango and citrus orchards or gardens, and near market places, at 75 sites located in 7 out of the 8 Kenyan provinces. As a result, more than 2000 specimens of this new fruit-fly species were caught in methyl-eugenol traps (not in Cue Lure). Surveys showed that the pest was present in most mango-growing areas, and that it also occurred in coastal forests (where it is probably able to reproduce in wild fruits). It was also observed that this new fruit fly was able to emerge from caged mango fruits. The strong and selective response of this new species to methyl-eugenol, and its capacity to infest and develop in mango fruits are typical for Asian fruit flies belonging to the genus Bactrocera. Therefore, it was felt that it was most probably an alien species introduced into Africa (Lux et al., 2003). Almost simultaneously in Tanzania, during a study done from June to September 2003 on fruit flies associated with mangoes, two species were found: Ceratitis cosyra (Diptera: Tephritidae – EPPO A1 list) and the same new species belonging to the Bactrocera dorsalis complex (Mwatawala et al., 2004). After these first records in Kenya and Tanzania, the presence of this new fruit fly species was reported from 9 other countries in Central Africa, attacking important fruit crops. In 2005, the pest was described as a new species originating from Asia (probably Sri Lanka) and called Bactrocera invadens (Drew et al., 2005), in order to reflect its rapid invasion of the African continent.
Bactrocera invadens (Diptera: Tephritidae – a new fruit fly species)
Why: Since 2003, a new fruit fly species, morphologically very similar to B. dorsalis, has been reported spreading rapidly in central Africa. This new pest is attacking mangoes, citrus and other tropical fruits. It was recently described and called Bactrocera invadens (Drew et al., 2005). Its finding in Sri Lanka confirmed its suspected Asian origin.
Africa: Benin (first found 2004-06), Cameroon (2004-07), Democratic Republic of Congo, Ghana (2005-01), Kenya (2003-02), Nigeria (2005-01), Senegal (2004-10), Sudan (2004-05), Tanzania (2003-12), Togo (2004-10), Uganda (2004-07). Its first place of discovery (i.e. Kenya) should not be assumed to be its point of entry into Africa, as it may have been overlooked in some areas.
Asia: Sri Lanka. B. invadens has been found in a collection of Dacini trapped during earlier surveys, so there was no indication of host plants or associated damage.
On which plants: Especially mango (Mangifera indica), but B. invadens is also found on guava (Psidium guajava), Citrus spp., papaya (Carica papaya), tomato (Lycopersicon esculentum), and some other wild African hosts (e.g. Strychnos spp.). Further studies are needed on the host range of this fruit fly, but it can be expected to attack a wide range of fruit crops.
Damage: In the preliminary findings in Kenya and Tanzania, it appeared clearly that mangoes were readily attacked by B. invadens and that it was competing strongly with Ceratitis cosyra. In infested mango samples, it was equally or even more abundant. However, as observations made are very recent, data is lacking on extent and severity of damage to the crops concerned. Considering its similarities with B. dorsalis, significant economic damage is expected.
Dissemination: Adults can fly but there is no data on their flying capacity. Trade of infested fruit can spread the pest. For the moment, there is no assumption on the pathway of introduction of B. invadens from Asia to Africa.
Pathway: Fruits of B. invadens host plants.
Possible risks: Although data is lacking on the biology of B. invadens and in particular on its potential to survive in more temperate regions, the recent example of B. zonata spreading in some countries around the Mediterranean Basin strongly advocates a cautious approach. In addition, citrus and tomatoes are mentioned as host plants and therefore could be immediately at risk in the EPPO region. The rapidity of spread and the probable large host range add to the risk. Control measures are probably available (e.g. male annihilation technique etc.) but for the moment, their efficacy is not known. It is desirable to prevent the introduction of such a new fruit fly species into the EPPO region.
EPPO RS 2005/085
Panel review date - Entry date 2005-06
Drew RAI, Tsuruta K, White IM (2005) A new species of pest fruit fly (Diptera: Tephritidae: Dacinae) from Sri Lanka and Africa. African Entomology 13(1), 149-154.
Lux SA, Copeland RS, White IM, Manrakhan A, Billah MK(2003) A new invasive fruit fly species from the Bactrocera dorsalis (Hendel) group detected in East Africa. Insect Science and its Application, 23(4), 355-361.
Mwatawala MW, White IM, Maerere AP, Senkondo FJ, Meyer M de (2004) A new invasive Bactrocera species (Diptera: Tephritidae) in Tanzania. African Entomology, 12(1), 154-156.
Conseil Phytosanitaire Inter Africain
Présence au Bénin d’une nouvelle espèce exotique de mouche des fruits (Diptera: Tephritidae). http://www.au-appo.org/fr/breve.php3?id_breve=11
IAEA website. Scientific and Technical Newsletter. Insect Pest Control Newsletter. The new invasive Bactrocera species. Insect Pest Control Newsletter, no.65, 18-20. http://www.iaea.org/programmes/nafa/d4/public/ipc-nl-65.pdf