Fruit fly research to improve market access

A future where mangoes do not require postharvest treatment to be exported into fruit fly-sensitive markets might one day become a reality, according to researchers from the Northern Territory Department of Primary industries and Fisheries (NTDPIF).

Their research program aims to develop, evaluate and implement a ‘systems approach’ protocol for market access as an alternative to chemical vapour heat or irradiation disinfestation treatments. This system considers fruit harvested at the hard green mature stage, and packing, grading, inspecting and culling processes to prevent ‘at-risk’ fruit from entering the supply chain.

Austin McLennan from the NTDPIF said that a ‘systems approach’ could achieve a similar or greater level of phytosanitary protection than a single postharvest treatment. “If we can prove the success of a ‘systems approach’ and develop alternative market access protocols that meet the requirements of international and domestic markets, there will be substantial benefits to industry. Our project will play a critical role in building the evidence base that could transform and underpin market access arrangements for Australian mangoes into the future. We are well on the way to gathering sufficient evidence to convince market access regulators that untreated mangoes can be imported without an unacceptable risk of importing new and unwanted fruit fly pests,” Mr McLennan said.

Mr McLennan’s research considered the annual fruit fly populations, investigated the impact of fruit maturity on host status and identified fruit defects that were a pathway for fly infestations, focussing on the properties in the Katherine and Mataranka region. Assessments of over 60,000 fruit confirmed that the risk of fruit being infested with pest fruit fly larvae was extremely low for this region. The few detections were attributed to the presence of overripe or damaged fruit in the sample.

“These few detections show the need for a greater understanding of the relationship between fruit fly risk and possible contributing factors such as fruit maturity and cultivar. We are now examining whether the findings can be applied to other production areas in Australia,” Mr McLennan said.

During the 2013 mango season, the level of fruit fly infestation was monitored in fruit collected from Darwin mango orchards. 4,500 Kensington Pride mangoes were analysed, which was considerably less than planned due to the poor season last year. The results suggested that the majority of infested fruit are those with some other predisposing defect, such as advanced ripening or broken skin, as documented in the Katherine work. An extensive trapping grid was deployed across three major production zones within the Darwin region to monitor seasonal activity of the Queensland fruit fly and Jarvis’ fruit fly (B. jarvisi).

“The data we gathered in the trapping studies will show us whether the underlying pattern of fruit fly activity in Darwin is similar to that observed in the Katherine / Mataranka region,” Mr McLennan said.

Controlled cage studies, where a set number of female flies are placed inside a cage around a bunch of fruit in the field, will play an important role in refining conclusions about the susceptibility of hard, mature mangoes to fruit fly. While the risk of infestation appears to be very low overall, this project is aiming to better understand the influence on host status of key factors such as variety and maturity/ripening status.

At the end of this coming season, it could be possible to have sufficient data to support the system’s approach for market access into protocoled markets. Future work will expand on these monitoring and collection activities, as well as resolving the fruit fly host status of major Australian mango cultivars and pilot new fruit fly systems.

This program is funded by voluntary grower contributions, Horticulture Australia Limited and NT DPIF. For more information contact Austin McLennan, NT Department of Resources, ph 0488 764 592 or email Austin.mclennan@nt.gov.au .