A quarantine treatment using bale compression (32 kg/cm² pressure) and phosphine fumigation (61 g/28.3 m³ aluminum phosphide for 7 d at 20°C) was approved to control Hessian fly, Mayetiola destructor (Say), in large-size, polypropylene fabric-wrapped bales exported from the western states to Japan. No Hessian fly puparia (45,366) survived to the adult stage in infested wheat, Triticum aestivum L., seedlings exposed to the treatment in a large-scale commercial test. Daily temperatures (mean ± SEM) inside and among bales in three test freight containers were 17.8 ± 0.2 front top, 17.0 ± 0.2 front bottom, 17.3 ± 0.2 middle bale, 15.7 ± 0.3 middle air, 18.5 ± 0.1 back top, and 18.1 ± 0.1°C back bottom, allowing the fumigation temperature to be established at ≥20°C. Mean fumigant concentrations ranged from 208 to 340 ppm during the first 3 d and ranged from 328 to 461 ppm after 7 d of fumigation. Copper plate corrosion values inside the doors, and in the middle of the large-size bales in all locations indicated moderate exposure to hydrogen phosphide (PH₃). PH₃ residues were below the U.S. Environmental Protection Agency tolerance of 0.1 ppm in animal feeds. The research was approved by Japan and U.S. regulatory agencies, and regulations were implemented on 20 May 2005. Compression in large-size bale compressors resulted in 3–3.6 and 0% survival of Hessian fly puparia and cereal leaf beetle, Oulema melanopus (L.), respectively. Bale compression can be used as a single treatment for cereal leaf beetle and as a component in a systems approach for quarantine control of Hessian fly.