Identification, biology, management and quarantine systems for fruit flies in Papua New Guinea

• National Agricultural Research Institute, Papua New Guinea

Fruit flies are a huge economic drain on countries where subsistence production or export markets are important features of the economy. In the Pacific region, crop losses ranging from 15 to 100% have been reported. Several fruit fly species of major economic importance are known to occur in PNG, including two (Bactrocera cucurbitae and B. papayae) which have been introduced from Southeast Asia. B. papayae can tolerate a wide range of climatic zones and so has the potential to affect crops in both the tropical lowlands and the cool highlands.

Observations in other countries have shown that these species and others found in PNG are likely to cause large losses in many fruit and vegetables cultivated there. However, the target crops and likely impacts have not yet been studied there. Given that current horticulture production in PNG is valued at about $1 billion per year, it is essential that the problem be addressed. In addition, the $400 million coffee crop is also susceptible to attack by the invading papaya fruit fly.

Fruit fly pests in PNG can easily spread into other South Pacific countries including, of course, Australia. There are, however, effective fruit fly monitoring and control strategies now available and, if applied on the basis of information gleaned from field research, these methods could contain the pest species before the situation worsens.

A further benefit of containment yet to be quantified comes from preserving tropical rainforests. Exotic fruit flies can invade rainforests, excluding fruit fly species native to the forest and thus possibly affecting pollination, seed dispersal and germination of endemic rainforest plant species.

The purpose of this project was to establish a fruit fly research and training program in PNG to protect crop production there and to prevent the spread of destructive fruit flies into other countries, including Australia.

The project was divided into five strands; the first of these involved determining the distribution of pest species in PNG and associated islands. Then, by analysis of results from trapping and host-rearing data, the team made risk assessments of the possible spread of the pest species found. The third strand tested the effectiveness of various control strategies against the identified pests, ensuring the suitability of methods for use in the field in PNG.

The fourth strand involved the development of quarantine procedures, including the establishment of early warning systems for exotic species entering PNG. Finally, the project team conducted a series of training workshops, designed to transfer research results to officers in PNG and elsewhere and to provide knowledge in specific areas.

The project achieved all objectives and made a significant contribution to the management of pest fruit flies in PNG. An excellent database on PNG fruit flies of economic importance has now been assembled. Scientists are trapping flies to monitor areas of particular quarantine relevance, in order to ensure that fly species not currently widespread in PNG are kept out of other areas.

In this connection the project has already picked up one serious incursion, which is the spread of the banana fruit fly to East New Britain. Previously it had been known only on the mainland where it was causing significant losses in banana. This is particularly significant because cooking and eating bananas are almost the only staple foods on East New Britain.

With the outbreak of banana fruit fly the project funded an experienced consultant to visit East New Britain to assess the problem, train field staff, undertake surveys to define the geographic limit of spread and introduce field pest control strategies. Without this intervention, many village households would have lost important cooking bananas which form their staple food supply.

The project has established a permanent fruit fly quarantine surveillance program in PNG to enable the early detection of new incursions of pest species from other countries. There are now in place emergency response procedures for the eradication of new exotic incursions should any occur. The project's important highlights are: a detailed knowledge of the fruit fly species of economic importance to PNG, their distribution and host plant range; an accurate assessment of the movement of fresh horticultural produce, by air travellers, from the PNG mainland to the island provinces and the Torres Strait Islands; demonstration of field pest control strategies to village, school and producer communities along with the management of the new outbreak of banana fruit fly in East New Britain.

PNG staff received sound training through extensive in-field collaboration and specific training workshops. As well, Mr Solomon Balagawi received an ACIAR John Allwright Fellowship to undertake postgraduate studies at Griffith University.