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.