2010 Annual Report 1a.Objectives (from AD-416) Conduct basic and commercial tests to determine the effectiveness of PH3, PH3+CO2, and modern compressors to control Hessian fly in single or combined treatments, and the effect of postharvest hay handling practices on Hessian fly mortality in the laboratory and field. 1b.Approach (from AD-416) Hessian fly will be reared in the greenhouse at the USDA, ARS, Parlier and Manhattan. Basic fumigation tests will be conducted in the facilities provided by the ARS in Parlier and the National Hay Association in California, Oregon, and Washington. Laboratory dose-response fumigation tests will determine the effect of temperature, exposure time, and PH3 or PH3+CO2 dosage on Hessian fly mortality, and establish a treatment schedule. Large-scale fumigation tests at hay handling facilities will confirm the efficacy of a proposed PH3 or PH3+CO2 fumigation schedule as a quarantine treatment. Bale compression tests at hay handling facilities will be used to determine the effect of compressors on mortality of Hessian fly puparia. Large-scale compression tests will be used to confirm the efficacy of bale compression alone or in combination with fumigation as a quarantine treatment. Basic tests will determine the effect of postharvest drying and bale curing on Hessian fly mortality. Data will be provided to The National Hay Association in support of market access for hay exports from the western U.S. Documents Trust with the National Hay Association. Log 38256. 3.Progress Report The agreement was established in support of of the in-house project Objective 3, to develop quarantine strategies to control Hessian fly in exported hay. Tests showed that fumigation of Hessian fly puparia, the stage of regulatory concern that may be found in weeds contaminating exported hay, might be controlled with a phosphine and carbon dioxide gas mixture dispensed from cylinders at a minimum dose of 750 ppm, temperature of 20°C (68°F) or higher, and duration of 4 days. Hay harvesting and drying practices can increase the mortality of Hessian fly puparia, especially in warm and arid climates where export quality hay is grown. The occurrence of Hessian fly puparia in exported hay from the western states is unlikely after this treatment. Test procedures using a high number of insects helps verify that hay handling techniques and postharvest treatments effectively reduce insect numbers that may occur in harvested hay. These investigations help support the concept that the occurrence of Hessian fly in harvested and processed, exported hay bales is negligible.