Recent developments in the disinfestation of Hessian fly puparia in baled hay
To comply with phytosanitary and quarantine regulations, baled hay has to be disinfested of Hessian fly [Mayetiola destructor (Say)] puparia before exporting to Japan. Several laboratory and field trials to destroy Hessian fly puparia in baled hay were either successful or unsuccessful. After the unsuccessful attempt to destroy Hessian fly puparia in the last confirmatory field test, laboratory tests were performed to identify any problem areas and validate the possible causes of insect survival during the field trials. Three different quantities of infested wheat seedlings contained in mesh bags designated types “A”, “B” and “C” test cages were used in the tests. Moisture content of the infested wheat seedlings contained in test cages was determined by the oven method. A recirculating forced-air dryer unit was used to determine the time required for the temperatures within the bulk of the infested wheat seedling to reach 60oC, and to confirm the thermal kill temperature for the Hessian fly puparia when the puparia were still located in the seedlings intact. Three thermocouple sensors were inserted into the bulk of the wheat seedlings to monitor the temperature. Three replicates were conducted for each test cage size. Heat disinfestation and control (unheated and heated) tests were conducted in a heat treatment unit on timothy hay bales. Thermocouple sensors were inserted into the bales and the wheat seedlings to monitor their temperature profiles. The heating time was influenced by the packing density of the infested wheat seedlings contained in the test cages. The survival of the Hessian fly puparia was influenced by the moisture content and the packing density of the infested wheat seedlings.
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