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Ethyl Formate-based System Approaches that Maintain Post-Harvested Citrus Quality and Control of Mediterranean Fruit Fly (Ceratitis capitata)
Doctoral Thesis   Open access

Ethyl Formate-based System Approaches that Maintain Post-Harvested Citrus Quality and Control of Mediterranean Fruit Fly (Ceratitis capitata)

Nelson Han
Doctor of Philosophy (PhD), Murdoch University
2024
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Open Access

Abstract

Mediterranean fruit-fly--Metabolism Mediterranean fruit-fly--Mortality Mediterranean fruit-fly--Effect of chemicals on Mandarin orange--Fumigation Mediterranean fruit-fly--Control
Mediterranean fruit fly (Ceratitis capitata) (Medfly) is considered one of the most destructive horticultural pests due to the damage it causes to fruit and vegetable produce, its wide host range, and its adaptability. There is an urgent need to develop and establish new fumigation procedures that effectively control Medfly and are environmentally friendly. This study investigated the mortality effect of ethyl formate in synergy with the nitrogen-modified atmosphere on the Mediterranean fruit fly (Ceratitis capitata) in mandarin fruits. This study used ethyl formate (EF) fumigation using the continuous purge flow method, effectively controlling the EF concentration within a specific concentration range. For 6 hours fumigation period, ethyl formate at a relevant low dose rate of 15-60 mg/L at 25 °C. After fumigation, mandarin fruit was exposed to 99% nitrogen in a hypoxic environment. Experimental results show that the second instar larvae and eggs are highly tolerant to EF, while the third instar larvae are more tolerant to nitrogen-controlled atmosphere (N2-CA) storage. The combined treatment of EF fumigation and N2-CA significantly increased the mortality of all stages. When the combined treatment method reached 100% mortality compared with a single treatment method, the treatment time of controlled atmosphere storage can be shortened by using a lower concentration of EF. In addition, this study evaluated the response of Mediterranean fruit flies in fruits to combined treatments and the physicochemical changes in the flavour profile of healthy Mandarin 'Imperial' (Citrus reticulata) after treatments. The experiment also found that low-concentration ethyl formate fumigation had no significant negative impact on the fruit's appearance, quality and flavour. To understand how this systems approach affects Medfly metabolism, we conducted at the metabolic profile level employing gas chromatography-mass spectrometry (GC-MS). C. capitata larvae treated with EF fumigation exhibited elevated levels of fatty acid ethyl esters such as ‘Ethyl 9-hexadecenoate’, ‘9,12,15-Octadecatrienoic acid, ethyl ester, (Z, Z, Z)-’, ‘Hexadecanoic acid, ethyl ester’ and ‘Ethyl Oleate’. A decrease in unsaturated fatty acids ‘9,12-Octadecadienoic acid (Z, Z)-’, and an increase in saturated fatty acids Oleic Acid were also detected. Identified that the appearance of fatty acid ethyl esters as the primary contributor to mortality changes under low oxygen stress. Our study revealed that a system approach based on ethyl formate fumigation and nitrogen-controlled atmosphere storage improved integrated postharvest pest management strategies for Medfly, enhanced consumer confidence in food safety, and enhanced the export competitiveness of local agricultural products.

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UN Sustainable Development Goals (SDGs)

This output has contributed to the advancement of the following goals:

#12 Responsible Consumption & Production

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