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

SIMPLE SUMMARY: Mealybugs (Hemiptera: Pseucoccidae) are frequently detected pests when importing fresh commodities. Ethyl formate, a methyl bromide alternative fumigant, has been applied to imported bananas in Korea to eliminate mealybugs, but it represents a considerable cost for production and management. A liquid ethyl formate treatment technology was newly developed to reduce the cost, and the efficacy of this technology against Planococcus citri, a highly important species of mealybug in Korea, was evaluated in this study. In addition, the effect of enhancing the control against P. citri was evaluated through the simultaneous treatment of ethyl formate and phosphine. The results show that, for the treatment with ethyl formate + nitrogen, the control effect did not decrease with the addition, and fruit damage did not occur as the nitrogen concentration increased. In the case of the combined treatment with phosphine, the control effect was greatly increased even when a small amount (0.1 g/m(3)) was applied. The results indicate that the new technology can be used to control mealybugs on banana fruits, and a combined treatment of ethyl formate and phosphine can also enhance the efficacy against mealybugs. ABSTRACT: Currently, the fumigant ethyl formate (EF) is stored as a liquified gas in metal cylinders mixed with carbon dioxide (CO(2)), 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(2)) 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(2) concurrent treatment applied to banana fruit was examined to evaluate the efficacy compared to the current EF + CO(2) product; and the increased efficacy with a phosphine (PH(3)) addition to EF + N(2) was also assessed. Concurrent treatment of EF and N(2) was performed at an LC(50) concentration of EF. N(2) 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(2) at 79%, and the color, sugar content, and weight loss of bananas were measured for 14 days after treatment. The EF with N(2) 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(3) showed a higher efficacy than treatment with EF alone, but only a slight increase in efficacy was observed when the PH(3) concentration increased. These results indicate that concurrent treatment with EF and N(2) can be used to control mealybugs on banana fruits, and combined treatment with EF and PH(3) can also enhance the efficacy against mealybugs.