## 4 Discussion  
Fumigation is a gas-type substance that quarantine pests in enclosed spaces and EF has been studied as quarantine fumigants to control various quarantine insect pests of commodities, such as fruits [21; 22; 23], vegetables [24], nursery plants [25], and mushrooms [17]. However, this fumigant EF was first studied to control general agricultural pests in vinyl houses instead of quarantining pests in quarantine containers. It is also known to have low mammalian toxicity and breaks down rapidly, thereby leaving no residues in the environment [18]. As a result, it was confirmed that the insecticide rate of more than 90% for SPW was established with a weak amount of 2 g m\({}^{-3}\) of ethyl formate in the YM vinyl house of the crop, and the YM had no phytotoxic damage. Therefore, our results showed EF fumigation has the potential to control SPW in vinyl houses cultivating YM plants. The fumigant has an insecticial effect when vaporized in a space sealed and exposed to insect pests in gaseous form, which means that the longer the exposure time, the higher the insecticial effect [26]. Furthermore, the fumigant uses the concept of CT (Concentration \(\times\) time) products to check the mortality relation against insect pests. Our result of EF efficacy to SPW showed LCT\({}_{90\%}\) of 2 h fumigation at a high concentration of EF was lower than the 12 h fumigation at a low concentration of EF. EF is a fumigant that is usually used on perishable commodities, such as fruits and vegetables alternative to MB [27], whose schedule was phased out due to the ozone-depleting effect under the Montreal Protocol [28], its phytotoxic damage to perishable commodities [29], and chronic toxicity to human [30]. EF is also used on stored grain to control stored grain pests, such as _Sitophilus oryzae_, _Tribolium castaneum_, and _Rhyzopertha domitica_[31] and is an alternative to phosphine (PH\({}_{3}\)) due to resistance causing the need for long exposure times [32]. Our experiment showed the first attempt to use EF for agricultural purposes, not just quarantine. Frequent use of insecticides or acaricides accelerates the development of resistance to these chemicals. For example, neonicotinoid insecticides, such as thiamethoxam and imidalcoprid, are commonly used to control whitefly and aphids, and resistance against these insecticides has been reported [33]. In addition, resistance to spinosad, frequently used to control thrips, has been reported [34]. However, insect resistance to EF has not yet been reported, which highlights the possibility of using EF as a greenhouse insect pest disinfectant in the future. Conventional insecticides are evenly sprayed throughout the vinyl house. However, these conventional methods cannot reach secluded spots, cracks, and crevices in the vinyl house or sometimes at the ventral leaf surfaces. On the contrary, EF fumigation can reach every out-of-the-way spot and every pest inside the fumigated vinyl house. Fumigation may also be safer for workers because they can avoid direct exposure to the gas. Thus, more studies are needed to evaluate the efficiency of EF fumigation at different developmental stages of various agricultural insect pests and to elucidate the phytotoxic effects of EF fumigation on various agricultural crop plants. To conclude, the results of this study offer new insight into using EF fumigation to totally or partially replace currently used spray insecticides or acaricides in protected farming of YM. In a previous study reported by [PERSON] et al. (2020) [35], ethyl formate did not show any phytotoxicity when they performed a fumigation study using a small chamber of 0.275 m\({}^{3}\). They also determined phytotoxicities on other agricultural crops, such as eggplant, crop peppers,and tomatoes, under the treatment of ethyl formate with two different exposure times of 2 and 4 h and complete control conditions on B. tabaci adults with 2.0 g EF/m\({}^{3}\) and 1.5 g EF/m\({}^{3}\), respectively [35].