Hydrogen Phosphide Residues and Efficacy To Control Hessian Fly (Diptera: Cecidomyiidae) in Compressed Hay for Export to Japan

Abstract

The response of Hessian fly, Mayetiola destructor (Say), puparia to 0.9- 6.4 g/m3 aluminum phosphide showed that higher mortality occurred at 20.0°C for 3 d at all doses tested than at 15.6°C for 4 d and that higher mortality was related to higher fumigant concentrations. A linear relation between dose and mortality was observed for both temperatures and durations tested, but complete mortality was not 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 multiplequarantine treatment that included compression (80 kg/cm2) and hydrogen phosphide fumigation (60 g/28.3 m3 aluminum phosphide) for 7 d at a constant mean temperature of 17.6°C or above to control Hessian fly puparia in compressed timothy hay, Phleum pratense , loaded in freight containers for export to Japan resulted in 118 survivors in 54,593 insects tested (99.784% mortality). Significantly higher numbers of puparia survived the treatment in the front bottom row of the freight container, where lower fumigant concentrations occurred. Copper-plate corrosion values, bale temperatures, and fumigant concentrations were similar throughout the freight container. Hydrogen phosphide residues 1 d after fumigation and overnight aeration in previous large-scale tests with six species of hay and in the large-scale test with timothy hay resulted in residues below the U.S. Environmental Protection Agency tolerance of 0.1 ppm.