## 4 Discussion  
To meet QPS regulations in Korea, we suggest that fumigation with PH\({}_{3}\) could be used as a viable alternative to MeBr treatment. Unlike MeBr, PH\({}_{3}\) effectively kills peach fruit moth larvae in Fuji apples while maintaining fruit quality according to the parameters measured in this study. [PERSON] (2000) reported a study on the comparison between MeBr and a 24 h treatment of PH\({}_{3}\) in which PH\({}_{3}\) did not induce apparent damage on pear but was not efficient to control _C. sasakii_[20]. In our study, 72 h treatment of PH\({}_{3}\) was required even at higher temperatures, but no damage was observed on apple. At lower temperatures, [PERSON] et al. (2010) reported that a longer period is required to control _Carposina niponensis_ with PH\({}_{3}\)[13]. Our study also supports this result, in which an 168 h treatment was not sufficient to eradicate _C. sasakii_ larvae at 5 \({}^{\circ}\)C. Although MeBr fumigation in apples is more time- and cost-effective compared with PH\({}_{3}\) fumigation, the MeBr residue on the fruit may be of concern; therefore, for natural reduction of bromide, a longer storage period at a lower temperature (>13 days at 2 \({}^{\circ}\)C following 2 h MeBr fumigation) might be required [21]. Besides, PH\({}_{3}\) fumigation normally leaves lesser residues that rapidly decreased after ventilation [22]. Phytotoxic damage, such as that shown by internal disorder and low flavor scores, was examined in \"Delicious\" and \"Spartan\" apple varieties after the recommended 48 g m\({}^{-3}\) MeBr fumigation for 2 h [4]. Depending on the apple variety, MeBr fumigation causes injuries such as water-core and internal breakdown in Fuji apples [23], and these apples exhibit similar symptoms in terms of changes to internal color and flavor. Although the same apple cultivar, \"Fuji\", was used in the present study, there might have been slight differences in terms of cultivation history and postharvest 1-MCP treatment. However, the identical scheduled MeBr fumigations elicited similar phytotoxic symptoms, such as softening and off-flavoring, in the current work. Fuji apples treated with 1-MCP, which was used to assess fruit quality in this study, show inhibition of ethylene synthesis with PH\({}_{3}\) treatment (unpublished data). It is expected that positive results could be yielded by commercial use of 1-MCP treatment followed by PH\({}_{3}\) fumigation in Fuji apples because, at the time of harvest in Korea, most apples are treated with 1-MCP prior to cool storage. Even though the cold treatment itself increased the shelf life of fruit and resulted in increased mortality in _C. sasakii_ larvae (up to 90% for 4 weeks of storage at 3 \(\pm\) 2 \({}^{\circ}\)C) in the present study, the treatment has limited use in QPS. Unlike metal phosphide fumigation, 72 h PH\({}_{3}\) gas fumigation can be considered as an alternative to MeBr fumigation for various perishable commodities that are stored at temperatures from \(-\)1.5 to 2 \({}^{\circ}\)C [10]. Although the efficacy of PH\({}_{3}\) fumigation against _C. pomonella_ larvae was not sufficiently demonstrated [10], we demonstrated its efficacy against _C. sasakii_ larvae in terms of insect mortality. Although limitations exist with PH\({}_{3}\) treatment in terms of temperature and time, PH\({}_{3}\) gas could act as a replacement for MeBr for the fumigation of apples exported from Korea because the former had no negative effects on the quality of Fuji apples. Due to the low negative effect on fresh commodities, more studies about PH\({}_{3}\) gas are processed to replace MeBr for quarantine purposes [24; 25]. Further studies are necessary to examine the relationship between PH\({}_{3}\) fumigation and low-temperature treatment in terms of the effects against _C. sasakii_, and such studies should ideally focus on demonstrating efficacy on a commercial scale. Conceptualization, B.-S.K., T.-H.K., B.-H.L. and S.-E.L.; methodology, B.-S.K., T.-H.K. and B.-H.L. ; software, B.-S.K. ; validation, B.-S.K., B.-H.L.