Technical Abstract: Quarantine control of Hessian fly, Mayetiola destructor (Say), by agricultural systems used to produce export quality hay for the Japan market was studied in the laboratory and field. Survival of Hessian fly puparia was evaluated under simulated seasonal weather conditions in incubators, regional open air drying, and in windrows of harvested hay in the Kittitas Valley and Columbia Basin of Washington, and the Central and Imperial Valleys of California. Exposure to field drying for three to six days caused insect mortality that ranged from very high to 100%. Mortality of 99.9% was attained, when extraordinarily high numbers of puparia were exposed to bale compression at 93 kg per sq cm in modern compressors that produce export size bales. Testing high numbers of insects confirms treatment efficacy, but Hessian fly is unlikely to occur in export quality hay fields. The combined effect of field drying and bale compression provides a negligible risk of Hessian fly in exported hay. A systems approach to mitigate the risk of accidental introductions of Hessian fly through shipments of U.S. hay will help alleviate the use of chemical fumigants on exported animal feed to achieve quarantine pest control.