HYDROGEN PHOSPHIDE RESIDUES AND EFFICACY TO CONTROL HESSIAN FLY (DIPTERA, CECIDOMYIIDAE) IN COMPRESSED HAY FOR EXPORT TO JAPAN

The response of Hessian fly, Mayetiola destructor (Say), puparia to 0. 9-6.4 g/m(3) aluminum phosphide showed that higher mortality occurred at 20.0 degrees C for 3 d at all doses tested than at 15.6 degrees C f or 4 d and that higher mortality was related to higher fumigant concen trations. A linear relation between dose and mortality was observed fo r both temperatures and durations tested, but complete mortality was n ot attained. The range in fumigant concentrations and mortality in all dose-response tests was 92.9-620.8 ppm and 85.6-99.3%, respectively. We attributed high mortality at the lower doses tested to desiccation of the puparia in the fumigation chamber. A large-scale test of the mu ltiple-quarantine treatment that included compression (80 kg/cm(2)) an d hydrogen phosphide fumigation (60 g/28.3 m(3) aluminum phosphide) fo r 7 d at a constant mean temperature of 17.6 degrees C or above to con trol Hessian By puparia in compressed timothy hay, Phleum pratense, lo aded in freight containers for export to Japan resulted in 118 survivo rs in 54,593 insects tested (99.784% mortality). Significantly higher numbers of puparia survived the treatment in the front bottom row of t he freight container, where lower fumigant concentrations occurred. Co pper-plate corrosion values, bale temperatures, and fumigant concentra tions were similar throughout the freight container. Hydrogen phosphid e residues 1 d after fumigation and overnight aeration in previous lar ge-scale tests with six species of hay and in the large-scale test wit h timothy hay resulted in residues below the U.S. Environmental Protec tion Agency tolerance of 0.1 ppm.