Ethyl Formate as a New Sanitary Treatment for Disinfesting the Hitchhiking Insect Pest _Halyomorpha halves_ on Imported Nonfood Agricultural Machinery  
and/or regulated pest groups (flies, moths, ants, and stinkbugs), which are primarily detected as hitchhiking on them [1].  
The brown marmorated stink bug (BMSB) _Halyomorpha halys_ (Hemiptera: Pentatomidae), one of the hitchhiking insect pests on imported nonfood miscellaneous goods, can cause severe agricultural damage [2] and urban and commercial damage because of its overwintering aggregations inside dwellings, vehicles, and assignments [3; 4; 5]. _H. halys_ has 300 species of host lists [6]. It occurs primarily in fruit orchards. When _H. halys_ is established, it rapidly becomes the dominant species, and, unlike native stink bugs such as _Plautia stali_ and _Riptortus pedestrians_, it is a pest that occurs throughout the entire growing season [7; 8].  
As the BMSB is controlled as a quarantine pest in certain countries, phytosanitary treatment of potential hosts such as plants and vehicles is essential to prevent its introduction and establishment. In particular, regarding the control of _H. halys_ hitchhiking on imports in Australia and New Zealand, fumigation with methyl bromide (MB) and sulfuryl fluoride, as well as heat treatment, has been approved [9]. In 2010, apple orchards in the mid-Atlantic region of the United States suffered a damage of USD 37 million due to _H. halys_ infestation, with the reported loss being >90% [10]. Furthermore, although _H. halys_ is not a major insect pest of grapes, several hectares of grape and peach fields were lost in the United States in 2010 because of high populations of _H. halys_ that appeared during the harvest season in the mid-Atlantic region [7; 11]. Heat treatment is approved at \(\geq\)56 \({}^{\circ}\)C at the coldest surface of the goods for 30 min or 60 \({}^{\circ}\)C for 10 min [12]; however, its use is limited because it is not cost-effective and is difficult to apply on large-sized goods such as agricultural machinery [13]. In addition, MB fumigation has been prohibited in some countries according to the Montreal Protocol because of its ozone depletion properties [14].  
Fumigation is primarily used in cases of stored grain infestation, soil pathogen and nematode control, and quarantine disinfectation [15; 16; 17]. It is an effective and economical disinfection method to control a broad range of insect pests in tightly sealed structures. Phosphine (PH\({}_{3}\)) is a promising alternative to MB, but it causes mechanical damage such as the appearance of solid crystalline encrustations on metal and metal-textile composites, including copper, brass, silver, and iron [18]. Conversely, ethyl formate (EF) is actively being investigated as an alternative to MB because it has non-ozone-depletion properties and provides a safer working environment than MB due to its relatively low toxicity to mammals and no-residue property on commodities [19; 20]. EF is generally available in liquid form and evaporates easily, eliminating the need for gaseous cylinders. Because of these advantages, studies conducted in recent years have reported that EF fumigation has been used for disinfection purposes for various types of fruits, vegetables, nursery plants, and even nonfood commodities [20; 21; 22; 23; 24; 25; 26; 27].  
In this study, we investigated the efficacy of EF application as a disinfectation treatment against _H. halys_, the major hitchhiking insect pest of imported agricultural machinery. Specifically, we conducted (1) an efficacy test of EF against _H. halys_ (>23 \({}^{\circ}\)C); (2) EF sorption and reactivity tests for the alternator, ignition coil, and starter motor, which are the major parts of agricultural machinery; and (3) a commercial trial using liquid EF with N\({}_{2}\) application against _H. halys_ on imported agricultural machinery.