Hessian fly puparia (37,167), Mayetiola destructor (Say), did not survive a large-scale commercial test (three freight containers) of a new quarantine treatment using compression (32 kg/cm²) and hydrogen phosphide fumigation (61 g/28.2 m³) for large-size, polypropylene fabric-wrapped bales of hay exported to Japan. Mean ± SEM temperatures in the large-size bales in different locations in the freight containers ranged from 18.0 ± 0.9 to 26.0 ± 1.3°C during the 7-d test conducted in a heated building at 20.1 ± 1.1°C. Highest concentrations of hydrogen phosphide in most locations in the freight containers were observed after 3 d of fumigation and ranged from 366.7 ± 96.1 to 425.0 ± 162.7 ppm (mean ± SEM) and throughout the 7 d of fumigation ranged from 253.6 ± 59.9 to 407.1 ± 76.5 ppm (mean ± SEM). Hydrogen phosphide residues after fumigation and aeration were <10 ppb and were below the U.S. Environmental Protection Agency tolerance of 0.1 ppm in animal feeds. The results of the test fulfills regulatory agency testing requirements and confirms the efficacy of the treatment to control Hessian fly in large-size, polypropylene fabric-wrapped bales of hay. Hessian fly puparia (2,160) did not survive a large-scale commercial test of compression (105 kg/cm²) and a 3-d hydrogen phosphide (60 g/28.3 m³) fumigation for standard bales.