Biocontrol introduction
Target pest: Araujia hortorum (Gentianales: Apocynaceae) = Araujia sericifera, moth plant
Agent introduced: Anastrepha australis (Diptera: Tephritidae) = Toxotrypana australis
Imported:
2020
Import source:
Uruguay
Import notes:
Landcare Research (2020j) - Anastrepha australis has been collected in Uruguay a number of times between 2010 and 2018, but laboratory rearing was initially unsuccessful due to limited numbers imported and asynchronous adult emergence in containment, and possibly poor host plant quality. A collecting trip from late-January to early-February this year [2020] resulted in over 80 pupae being imported into containment. So far, rearing of the new colony has been successful.
Waikato Regional Council (2023) - Anastrepha australis larvae were collected from developing A. hortorum pods collected in the Punta de Rieles neighbourhood of Montevideo, Uruguay, in January 2020 and imported into containment in New Zealand in February 2020. Host range experiments were conducted from 2020 to 2021 on the colony resulting from this importation. If A. australis is released in New Zealand, all individuals released will be progeny of this founding population.
Impacts on non-targets:
Landcare Research (2020j) - so far host range tests have been conducted on swan plant (Gomphocarpus fruiticosus), on which females showed no interest in oviposition. Further host plant testing will be done this summer [2020-21].
Waikato Regional Council (2023) - Araujia hortorum (family Apocynaceae, subfamily Asclepiadoideae) is the only representative of the genus Araujia in New Zealand. There are only three native species in the same family, all in the genus Parsonsia (subfamily Apocynoideae). No-choice host range tests were conducted on eight plant species representing four tribes and two subfamilies of the Apocynaceae: two native Parsonsia species and six ornamental plant species (including A. hortorum). Development to pupae occurred in approximately 60% of replicates of A. hortorum and 40% of replicates of Oxypetalum coeruleum (tweedia) (both in the subtribe Oxypetalinae). No pupal development or any signs of oviposition or damage occurred on any of the other test plant species. It is highly likely that A. australis is host specific in the subtribe Oxypetalinae. In fact, laboratory host range testing can overestimate the field host range, and A. australis (and A. nigra and A. proseni, which are now considered conspecific with A. australis [see taxonomic note (23 April 2023) in ‘General comments’ section]) have only ever been recorded from plant species in the genus Araujia in the fruit flies' native range, even though O. coeruleum occurs within that range. Nevertheless, the possibility of non-target attack on O. coeruleum in New Zealand cannot be ruled out. However, if it occurs, damage to pods is likely to be inconspicuous and will not affect the ornamental properties of the plant. The risk of significant damage to native plants in New Zealand is negligible.
General comments:
Taxonomic note (19 April 2023) - the following information is from Waikato Regional Council (2023). Seven species of fruit fly recognised as the ‘curvicauda species group’ were previously included in the genus Toxotrypana, including T. australis (currently Anastrepha australis). Molecular studies reported in 2017 resulted in Toxotrypana being synonymised with Anastrepha. Although Toxotrypana is the senior name, Anastrepha took precedence due to the much greater economic importance of its species. The fruit flies imported into containment in New Zealand in February 2020 showed some variability in colour; however, molecular investigation indicated all individuals were A. australis. Specimens were sent to an overseas expert who found that the external features of flies in culture in New Zealand match the descriptions of three Anastrepha species in the curvicauda group, but molecular work again indicated they were all the same species. That expert also considered it likely that all the species that Blanchard described under Toxotrypana, except littoralis, are colour morphs of the same species, and noted that Anastrepha nigrotaenia (Enderlein) appears to be the valid name for this species, although the taxonomy needs to be revised. Therefore, while the name A. australis will be used for now for the New Zealand material, the name is likely to change to A. nigrotaenia once a taxonomic revision has been completed and formally accepted.
References
Landcare Research (2020j). A seed-damaging fly for moth plant? Weed Biocontrol: What's New? 94, Nov 2020. https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/a-seed-damaging-fly-for-moth-plant
Waikato Regional Council (2023). Application to EPA (APP204305) to release a new organism, the moth plant fruit fly, Anastrepha australis. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/APP204305/APP204305-Application-.pdf
