Application to release moth plant fruit fly

Image – Carolyn Lewis

The moth plant fruit fly, Anastrepha australis, is a large fruit fly that attacks the fruit pods of moth plant. Female flies lay eggs inside the pods and the larvae feed on the developing seeds. This destroys the inside of moth plant pods and no seeds form. Without seeds, the weed cannot spread and increase in density.

The application seeks approval to introduce the moth plant fruit fly into New Zealand to help control moth plant.

Background

The application has been submitted by Waikato Regional Council, acting on behalf of the National Biocontrol Collective, a consortium of regional councils and the Department of Conservation. The Collective funds the development of weed biocontrol programmes in New Zealand. Manaaki Whenua - Landcare Research has provided the science, has prepared and is managing the application process, including consultation with EPA and stakeholders. Waikato Regional Council is managing Maori consultation and engagement.

In its native range, moth plant is considered to be an ornamental, industrial and medicinal plant but in its exotic range these benefits are heavily outweighed by its environmental impact. In New Zealand moth plant climbs over shrubs and small trees, smothering and breaking them down. It also spreads over the ground, shading out regenerating seedlings and low native vegetation. Moth plant is known from intact and disturbed forest and forest margins, tracks, coastline, cliffs, riparian margins, shrublands, mangroves, inshore and offshore islands; almost any frost-free habitat.

Both fruits and stems exude a caustic milky sap when broken. This white latex is sticky, and causes skin or eye irritation in susceptible people. The latex is poisonous (Landcare Research accessed 2011) and ingestion of the foliage of Araujia hortorum can cause gastrointestinal symptoms such as nausea, vomiting and diarrhoea. Other plant parts including seeds have been reported as toxic to poultry and cattle in Australia, though it is not often eaten and cases of poisoning are not common.

For more information about moth plant see:

• Ecology and pest status of moth plant

The moth plant fruit fly is the third natural enemy to be considered for biocontrol of moth plant. The EPA approved the release of the moth plant rust Puccinia araujiae in 2015 and the moth plant beetle Freudeita curpripennis in 2018. The larvae of the moth plant beetle feed on the roots of the weed and the rust has not yet been released due to issues with importing it from Argentina. The moth plant beetle was released in 2019. We expect the moth plant fruit fly to complement the damage of the beetle leading to a greater impact on the weed.

Identification and assessment of risks, costs and benefits

The potential risks, costs and benefits associated with the proposed introduction of the moth plant fruit fly to New Zealand and the possible reduction in the abundance and vigour of moth plant have been identified by literature review and by consultation with stakeholders.

• Risks, costs and benefits of moth plant biocontrol

The application addresses in detail the significant adverse and the beneficial effects identified (highlighted in bold). The potential benefits of biological control will be the mitigation of the adverse effects of moth plant on the New Zealand environment. The key potential adverse effects relate to impacts on native flora and fauna. These are addressed fully in the application:

• direct damage to valued garden ornamentals especially tweedia
• direct damage to native plants
• indirect effects on flora and fauna as a result of disruption of ecological relationships

Moth plant belongs to the sub family Asclepiadoidieae of the family Apocynaceae. This was previously a separate family Asclepiadaceae. There are no native species in this sub-family, and the application presents evidence that no native species will be at risk from this fly. Several ornamental species are related to moth plants, notably tweedia (Oxypetalum coeruleum). This is particularly valued by those fostering butterflies such as monarchs.  Tests indicate that this plant could be at risk from incidental attack by Anastrepha australis. The social and economic costs associated with possible attack on tweedia will be canvassed and addressed in the application. The results of that consultation are presented in the application. 

Because the fruit fly is almost host specific, population densities capable of interacting significantly with other plants or animals will only be found in close proximity to moth plant. Mechanisms for interaction are limited. As a result, no significant disturbance of ecological relationships is expected in New Zealand.

Pre-application consultation with Iwi

The members of Te Herenga, the EPA's national network, were contacted in September 2021 and invited to enter dialogue on plans to apply to the EPA to introduce another biocontrol agent for moth plant.

The message to Te Herenga described how the applicant intends to assess the risks, costs and benefits associated with the proposed introduction. Members were invited to identify any issues that they would like to be addressed in the application. Further consultation was undertaken by Waikato Regional Council. All responses specifically related to the proposed introduction of the moth plant fruit fly were summarised in the application (see link below).

At the request of the applicant, the EPA convened a reference group from Te Herenga to meet and discuss the issues surrounding the proposed applications. The application addresses principles identified in that report.

• Report of the reference group concerning biological control of weeds

Pre-application consultation with other organisations

Other organisations were consulted in the course of preparing the successful 2015 (P. araujiae) and 2018 (Freudeita cupripennis) applications.These organisations and stakeholders were consulted again to support this application. They include:

• New Zealand Plant Producers Inc.
• Regional Councils
• Royal Forest and Bird Protection Society of New Zealand
• Department of Conservation staff
• QEII National Trust
• NZ Landcare Trust
• NZ Entomological Society
• NZ Plant Protection Society

All responses specifically related to the proposed introduction of the moth plant fruit fly were summarised in the application (see link below).

Key documents

Reports on host-range determination

Safety issues are paramount in the minds of biocontrol of weeds researchers. Researchers rigorously test all proposed agents to assess the risk of damage to non-target plants. A set of procedures helps researchers choose a suitable shortlist of test plants, and this methodology is now well-accepted internationally. The results of host range testing conducted on the moth plant fruit fly is fully discussed in the application. The report of these results can be found here:

• Host range testing of Anastrepha australis

The unpublished report will be peer reviewed and that review will be provided to EPA.

Cited references

Waipara, N.W., Winks, C.J., Gianotti, A.F., Villamil, C.B., Villamil, S.C., Delhey, R., Kiehr, M., Traversa, M.G., Carpintero, D.L. (2006) Surveys for potential biocontrol agents for moth plant in New Zealand and Argentina. New Zealand Plant Protection 59: 1-6.

Winks C.J., Fowler, S.V., (2000) Prospects for biological control of moth plant, Araujia sericifera Asclepiadaceae). Landcare Research Contract Report LC9900/100. Landcare Research, Lincoln, New Zealand. 18 p.

Link to application

Application to release moth plant fruit fly Araujia hortorum (syn. of Araujia sericifera).