Implementing brown sugar flotation (BSF) for assuring freedom of fruit from Qfly (CY16011)

What was it all about?

Cherries are subjected to strict quarantine treatments in order to access fruit fly sensitive markets, both interstate and overseas. Previous Hort Innovation Cherry Fund project Evaluation of the sugar flotation method for testing cherries for Queensland fruit fly (CY14009) demonstrated that brown sugar flotation offers a quick and easy way to check for the presence of eggs and larvae in cherry fruit. This project, which ran from 2017 to 2019, further refined brown sugar flotation for cherries for implementing the process commercially.

Initial testing of the brown sugar flotation method took place in the lab, checking the amounts of materials that would be required by growers to conduct each test. From this, the researchers developed an initial set of training materials.

Trials conducted by the NSW Department of Primary Industries (NSW DPI) demonstrated that the solution needed to be at least 16°Brix for eggs to float. It was also found that the solution could be made several weeks in advance and cold stored, as the time between adding solution and examining for eggs and larvae was not critical. Ensuring cherries were thoroughly crushed maximised recovery of eggs and larvae.

A standardised procedure was developed and then adapted for implementation on farm. During the project, NSW DPI developed a protocol for application of brown sugar flotation as part of a trial systems approach to access markets in fruit fly free South Australia.

The protocol, testing 600 fruit sampled from each registered block, twice during the season, was implemented. Brown sugar flotation was used on over 17,000 cherry fruit from New South Wales and over 3000 cherry fruit from Victoria during the 2018/19 season. No Queensland fruit fly eggs or larvae were detected.

The revised procedure has been provided to the cherry industry along with identification guides for use during the process. In addition, a short instructional video, available here, was made to demonstrate the process and further assist growers and packers to identify fruit fly larvae.