Development of a Concurrent Treatment Technique of Ethyl Formate and Mixtures (Nitrogen, Phosphine) to Control Citrus Mealybug ().

Currently, the fumigant ethyl formate (EF) is stored as a liquified gas in metal cylinders mixed with carbon dioxide (CO), but this product type is expensive to manufacture, transport, and maintain in cylinders. To address these problems, we developed a new EF fumigation technique with a nitrogen (N) carrier. In this report, the susceptibility of citrus mealybugs, one of the most resistant mealybugs to fumigants, to EF was assessed; the phytotoxicity of an EF + N concurrent treatment applied to banana fruit was examined to evaluate the efficacy compared to the current EF + CO product; and the increased efficacy with a phosphine (PH) addition to EF + N was also assessed. Concurrent treatment of EF and N was performed at an LC concentration of EF. N was applied in seven doses from concentrations of 79% to 95%. The phytotoxicity of EF to bananas was assessed by applying EF at 35 mg/L with N at 79%, and the color, sugar content, and weight loss of bananas were measured for 14 days after treatment. The EF with N treatment resulted in more than 50% mortality at all growth stages of the mealybug, and there was no significant difference between the untreated and treated banana fruits. EF mixed with PH showed a higher efficacy than treatment with EF alone, but only a slight increase in efficacy was observed when the PH concentration increased. These results indicate that concurrent treatment with EF and N can be used to control mealybugs on banana fruits, and combined treatment with EF and PH can also enhance the efficacy against mealybugs.