Postharvest efficacy and phytotoxicity of fludioxonil on Australian citrus (CT06026)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

The Australian citrus industry had an export potential of over 160 million dollars annually, mostly in fresh packed navel oranges, but also easy peel mandarins and lemons. The maintenance of export markets was of vital importance to the survival of an industry that had overcome a number of obstacles to increase its market share. The main issues surrounding continued export of fruit was the expectation that fruit would be free of pests and disease. There was also an expectation that fruit treatments should be ‘greener’. The previous few years had seen an increase in decay levels at markets end. In an attempt to address this the industry had focussed on overall ‘best practice’ strategies such as sanitation and improving technologies for fungicide application. The issue with this was that the industry, despite improving its overall strategies for decay control, had been hindered by the lack in availability of registered fungicides (limited to benzimidazole and imidazole based fungicides at the time). An over reliance on limited number of fungicides raised the potential for increased resistance to these established postharvest fungicides and placed valuable export markets at risk.

The main aim of this project was to review a possible third chemistry - fludioxonil, for use by the Australian citrus industry. A new chemistry would fit into packingshed systems that were continually improving packingshed postharvest processes with little disruption to practices used at the time. The main benefit to industry if a new chemistry became available was a further decrease in the amount of decayed fruit reaching export destinations.

The aims were addressed by the following activities:

• Efficacy evaluation of fludioxonil on the main citrus pathogens on three cultivars, navel orange, mandarin and lemon.
• Examination of any phytotoxic effects of fludioxonil on navel oranges, mandarins and lemons.
• Comparing efficacy and phytotoxicity of fludioxonil with current citrus postharvest fungicides and fungicide exposure times.