## 1 Introduction  
Sweet-potato whitfely (SPW, _Bemisia tabaci_) was an insect pest with more than 900 host species, including various fruit vegetables globally [1]. SPW has more than 24 biotypes, including B and Q biotypes (B-ty and Q-ty), which were the most harmful and hard to control among the biotypes in vinyl house cultivation [2]. Since the first occurrence of B-ty in Korea in 1998 [3, 4], it has spread throughout the southern area of Korea in 2005 [5].  
Yellow melon (YM) is one of the major fruit vegetables grown in a vinyl house in Korea [6], cultivated in about 7633 ha of vinyl house area and occupying 14% of the total domestic vinyl house average [7]. In YM cultivation in vinyl houses, SPW is one of the virus vectors that damage plants by sucking the sap from plant leaves, thus making the leaves shiny or with blackened sooty mold by producing honeydew. The income loss by the infestation of SPW was estimated as 5% (30 million USD annually) of the total income of farmers (612 million USD/7633 ha) in Korea, while farmers used 28 million USD for its control annually [7; 8].  
Although many insecticides, such as organophosphates, carbamates, pyrethroids, insect growth regulators, and neonicotinoids have been developed to control SPW, it experienced difficulty in becoming resistant due to indiscriminate use and the short generation time of the species [9; 10]. Furthermore, current pesticides such as spinosad and imidaloc-prid to control SPW in vinyl houses are restricted during the fertilization season due to pollinators, such as honeybees [11]. Moreover, the application of pesticides was restricted due to the enforcement of maximum residue limits (MRLs) for registered pesticides and the introduction of a positive list system that regulated residues of 0.01 ppm for unregistered pesticides on various crops [12].  
Another difficulty in applying insecticides for controlling SPW is the even distribution of the chemicals to every niche of the SPW [13]. As a result, the insecticides sprayed cannot reach every SPW target, especially those living on the undersides of leaves. Therefore, new pesticides and new application techniques must ensure effective and strategic pest management with consumer safety in controlling SPW in vinyl house farming. Through our previous studies, ethyl formate (EF) was currently recognized with the possibility to control insect pests on fruit vegetables in terms of having less issues, with no residues in final production [6].  
EF is a naturally occurring substance in cheese, orange, and soil [14]. It is currently used in quarantine as an alternative to methyl bromide (MB) due to its insecticidal effect against stored insects [15], aphids [16], and flies [17]. EF was also used as an alternative to phosphine, which requires long usage in controlling stored grain insect pests due to its valuable attributes, such as its total control of insects [18]. Additionally, there are no regulations concerning residues using EF since it has been used as food additives such as flavoring agents for a long time and classified as \"Generally Recognized as Safe\" by the Food and Drug Administration of the USA [19]. Due to post-fumigation customer safety on numerous commodities, including fruits and vegetables, EF and its application have been adopted as alternative options in the chemical disinfestation method in quarantine and the post-harvest section.  
Thus, we first evaluated the possibility of agricultural use of EF, especially during the growing season of YM in vinyl houses. In this research, we conducted (1) a preliminary study on insecticidal efficacy of EF fumigation to SPW adults in desiccators and phytotoxicity assessment of EF fumigation on yellow melon plants in small chambers, (2) a scaled-up study on insecticidal activity and phytotoxicity assessment of EF fumigation in a medium-size vinyl house, and (3) a field study using practical field trials on the efficacy of EF fumigation in farmers vinyl houses.