This study investigated an alternative fumigant for imported sweet pumpkin. Laboratory fumigations with ethyl formate (EF) and phosphine (PH₃) alone and in combination were conducted at different temperatures in 12-liter desiccators to determine their efficacy and synergism against adults and eggs of two-spotted spider mites (Tetranychus urticae Koch), a major pest of sweet pumpkins; larger scale fumigations with EF were also performed to evaluate the impact of EF fumigation on the postharvest quality of sweet pumpkin and EF absorption. EF fumigation of 4 h achieved 100% control of both adults and eggs at 10°C. Efficacy of EF also increased with temperature. Conversely, PH₃ fumigation for 4 and 6 h was not effective against either adults or eggs, and no synergism between EF and PH₃ was observed. In larger scale fumigation tests, EF at 60 g/m³ for 4 h resulted in 100% control of both adults and eggs at 10°C, without causing injury to the sweet pumpkins. These results suggest that EF has the potential to be a safe and effective alternative to methyl bromide fumigation for controlling two-spotted spider mites on sweet pumpkin.

Citrus mealybug, Planococcus citri (Risso), is a known quarantine pest that is difficult to control with phosphine (PH₃) or low concentrations of ethyl formate (EF), particularly at low temperatures. Methyl bromide (MB) is a fumigant used for quarantine and preshipment (QPS) that can eradicate target pests with short fumigation periods. However, MB, which is an ozone-depleting substance, is scheduled to be phased out in South Korea over the next decade. There is no ideal alternative fumigant to replace MB for QPS of perishable commodities. A laboratory study was conducted to compare the individual effects of EF and PH₃ individually, and the effects of EF mixed with PH₃ as an MB alternative for the control of P. citri adults, nymphs, and eggs. In comparison to treatments with EF and PH₃ individually, EF mixed with PH₃ resulted in high toxicity to all stages of P. citri. The eggs were more tolerant than the nymphs and adults. A mixed treatment of EF and PH₃ achieved complete control of eggs infesting pineapples at concentrations of 25.1/1.0 (EF/PH₃) mg/liter at 8 °C for 4 h of exposures. This new combined EF/PH₃ fumigation technology could offer shorter exposure times and less damage to perishable commodities at low temperatures, and could potentially be extended to controlling other quarantine pests as a replacement treatment for fruit and vegetables in which methyl bromide is currently being used.