## 1 Introduction  
Grapes are a major temperate fruit group worldwide, with a total trade of $11 billion in 2020, and the top exporters and importers are Chile ($1.18 billion) and the United States ($1.36 billion) [1]. In the same year, the Republic of Korea imported 70,932 t of grapes valued at $212 million, and 2108 t valued at $31 million were exported [2]. During the export or import of grapes at Korean ports, they are usually fumigated with methyl bromide (MB), as per the present phytosanitary treatment protocols [3]. However, MB is an ozone-depleting substance and a highly toxic pesticide, making it necessary to find an effective alternative [4, 5]. MB also causes acute or chronic toxicity, posing a health risk for workers [6, 7, 8, 9]. Exposure to concentrations above the permissible 1 ppm limit causes functional degradation of the nervous system in workers [10, 11, 12]. Therefore, the International Plant Protection Convention (IPPC), as a representative organization in quarantine worldwide, recommends replacing MB or reducing its use as a phytosanitary measure [13]. Ethyl formate (EF), known as a safer fumigant for workers and consumers, was designated a \"generally recognized as safe\" material status by the Food and Drug Administration and is also used in the manufacturing of food flavoring and no-residue commodities [14]. Furthermore, the time-weighted average threshold limit value (TLV for a 40-h workweek/8-h workdays) as the exposure limit of EF is 100 ppm, which is considerably-higher than the 1 ppm limit of MB TLV [15]. Hence, EF is safer and more controllable than MB in terms of maintaining exposure below the limit [16]. In Korea, approximately 41 t of MB was used to treat fruits in quarantine in 2021, which is almost 10 percent of the total MB consumption. A total of 258 t of EF was used for fruits during the same period. However, grapes cannot be fumigated with EF as there are no EF guidelines for grapes [17]. From 2007 to 2011, the major quarantine pests on grapes imported into Korea were mealybugs and scale insects [18]. During the export inspection of grapes, _Planococcus_ sp. and insects of the family Pseudococcidae were found [19], with reports of restrictions on exports to China, Thailand, and Australia [20]. Recently, EF has been reported as a potential fumigant to replace MB due to its insecticidal effect on different quarantine pests found on perishable commodities, such as bananas, oranges, dry dates, blueberries, and even non-food commodities with less than 4 h of shelf-life [21; 22; 23; 24; 25]. EF was specifically effective in disinfesting mealybugs and scale insects and had an efficacy similar to that of MB [26; 27; 28; 29; 30]. However, it is difficult to adapt EF liquefied with CO\({}_{2}\) in high-pressured heavy steel cylinders for commercial use in terms of cost and handling. Hence, liquid EF in plastic casing could be a safer and more cost-effective alternative for liquefied EF in cylinders [21; 22]. In this study, the feasibility of EF as an alternative to MB for mealybugs on grapes (Campbell Early, a major variety of grapes in Korea) was evaluated as follows: (1) The efficacy of EF in the egg and adult stage of _Pseudococcus comstocki_ (Kuwana) was evaluated in small-scale laboratory trials. This has not been done in previous studies. (2) The grape sorption and permeability of EF were analyzed to determine the appropriate loading ratio and box types for the grapes. (3) Commercial scale trials using 10 m\({}^{3}\) containers were conducted using eggs of the Comstock mealybug (_P. comstocki_) at a tolerant stage. (4) Concentrations of EF desorbed from treated grapes were monitored under simulated storage condotitons of a container and warehouse for 72 h after fumigation completion for comparison with MB. This process generally takes place before the delivery of grapes to consumers. (5) The effect of EF fumigation on the abscission rate, decay rate, sugar content, hardness, tittatable acidity, and weight loss of grapes was assessed.