HESSIAN FLY (DIPTERA, CECIDOMYIIDAE) MORTALITY RELATED TO MOISTURE, SEASON, TEMPERATURE, AND HARVESTING PRACTICES FOR COMPRESSED AND FUMIGATED HAY EXPORTED TO JAPAN

A significant reduction in mortality of Hessian fly, Mayetiola destruc tor (Say), puparia was related to moistening infested wheat seedlings with water before exposure to a multiple-quarantine treatment of compr ession (72 g/cm(2)) and hydrogen phosphide (60 g/28.3 m(3) aluminum ph osphide) fumigation for 7 d in compressed hay for export to Japan. Mor tality of puparia in laboratory tests was higher after a 3-wk exposure and significantly higher after exposures of 1, 2, and 4 wk to simulat ed summer (28 degrees C days, 22.5 degrees C nights; photoperiod of 12 :12 [L:D] h; and 42-45% RH) versus simulated spring-fall conditions (2 5 degrees C days, 12.5 degrees C nights; photoperiod of 12:12 [L:D] h; and 60-65% RH) in laboratory tests. Mortality was higher in puparia e xposed for 3-4 d than in those exposed for 1 d to 32.1, 34.9, or 37.7 degrees C days, 23.8 degrees C nights; and a photoperiod of 10:14 (L:D ) h in laboratory tests. Hessian fly puparia did not survive field dry ing alone or in combination with any hay-harvesting practice including windrowing, baling, curing, or compression under normal seasonal temp eratures in the field. We propose exposure of infested wheat seedlings to 25 degrees C for 7 d before treatment as a method to fulfill regul atory agency requirements of no survivors in large-scale tests.