## 4 Discussion  
The applications of EF for controlling various pests such as scales [28], mealybugs [27; 35], thrips [36], aphids [37], mites [38], and flies [39] have been studied. However, determining the LCt99 of EF for _P. comstocki_ during quarantine was first done in this study. To develop the phytosanitary disinfection measures associated with new pests using fumigants, several tests are necessary, including efficacy data under laboratory and operational conditions [40]. Based on the LCt99 value of EF on _P. comstocki_, the sorption rate of EF to grapes, and large-scale tests, we revealed that _P. comstocki_ was completely killed using EF at 70 g/m\({}^{3}\) for 4 h, 5 \({}^{\circ}\)C, 145.85 g h/m\({}^{3}\), with a loading ratio of 10%, without any phototoxic effects on grapes (Campbell Early). The sorption rate of a commodity depends on the fumigants used. Therefore, it is critical for determining the dosage of fumigants for disinfection of target pests [21; 31; 41; 42]. In the present study, a higher loading ratio (20%) showed more sorption on the grapes than a lower loading ratio (10%), similar to the results of a previous study involving the use of EF on fruits and nursery plants [30; 43; 44]. Nevertheless, the 10% loading ratio did not prevent the attainment of the LCt99 on the target pest in the large-scale (commercial) trials (Table 2). This suggests that a loading ratio of 10% on grapes is appropriate for commercial application. Packing materials can affect the efficacy of the fumigant for pests by blocking access to the commodity. For example, the EF concentrations inside bags of bananas were considerably lower than those outside the bags [21]. The mortality of _Planococcus citri_ eggs also decreased significantly under bagging. However, the EF concentration did not significantly differ inside and outside the packaging film in grapes (Figure 3), as the film is permeable enough to allow EF gas to penetrate. The current packaging of grapes was applied in the large-scale trials to evaluate commercial feasibility. A few previous studies have investigated the efficacy of EF on mealybugs. The LCt99 of EF on _Planococcus citri_ eggs at 8 \({}^{\circ}\)C was calculated to be 211 g h/m\({}^{3}\), whereas that on nymph and adults was 49.5 and 124.6 g h/m\({}^{3}\)[30]. For grape mealybugs (_Pseudococcus marituimus_), the EF LCt99 value on eggs and adults was estimated at 160.2 and 58.1 g h/m\({}^{3}\) at 24 \({}^{\circ}\)C [26]. In the present study, the LCt99 of EF was 145.85 g h/m\({}^{3}\) on _P. comstocki_ eggs and 47.36 g h/m\({}^{3}\) on _P. comstocki_ adults. This result is consistent with a previous study that showed that the eggs of mealybugs were more tolerant towards EF fumigation, compared with mealybugs at other stages. The CT product in scale-up trials with a loading ratio of 20% was 114.8 g h/m\({}^{3}\), which is lower than the LCt99 on _P. comstocki_ eggs; therefore, it is justified that not all _P. comstocki_ specimens were killed. We confirmed that EF application at 145.85 g h/m\({}^{3}\) with a loading ratio of 10% can disinfect mealybugs completely. The assessment of phytotoxic effects of EF on Thompson Seedless 30 d post-fumigation (5% EF for 2 h, 10% loading ratio, expected Ct product >100 g h/m\({}^{3}\)) showed that there was no stem browning, bleaching, abscission rates, or decaying, except for small differences in rachis browning [26]. In the present study, similar conditions were provided during assessment except for temperature (25 \({}^{\circ}\)C), and the results were also similar in terms of physical quality factors such as abscission and decaying. We found that internal factors such as the sugar content and titratable acidity were not altered by EF fumigation. Recent reports on the use of EF treatment on sweet persimmons showed similar results with respect to the lack of phytotoxic damage and internal quality factors [45]. Thus, EF can be effectively used for fumigation without the concern of phytotoxic damage or alterations in internal quality factors.