Complete Mortality of Hessian Fly (Diptera: Cecidomyiidae) Puparia in Two Large-Scale Tests To Confirm the Efficacy of a Multiple Quarantine Treatment for Compressed Hay Exported to Japan

Abstract

Hessian fly, Mayetiola destructor (Say), was reared in a greenhouse in Fresno, CA, to eliminate interstate shipments of test materials. Two large-scale tests fulfilled regulatory test requirements for control of Hessian fly in compressed hay for export to Japan. We confirmed the efficacy of a multiple quarantine treatment (≥80 kg/cm 2 compression and 60 g/ 28.3 m 3 aluminum phosphide for 7 d at 22°C). A large-scale test with timothy, Phleum pratense, hay and a 2nd test with alfalfa, Medicago sativa, combined with Sudan grass, Sorghum bicolor sudanensis, hays loaded in 76.2-m 3 freight containers resulted in complete mortality of 38,957 and 37,345 Hessian fly puparia, respectively. These species of hay were representative of previously tested species including oat, Avena sativa, and Bermuda grass, Cynodon dactylon, hays and rye straw, Secale cereale. Copper plate corrosion values, bale temperatures, and fumigant concentrations were similar throughout the freight containers in both tests. Lower fumigant concentrations in the 2nd test than in the 1st test were attributed to leakage. Hydrogen phosphide residues 1 d after fumigation and overnight aeration resulted in concentrations below the U.S. Environmental Protection Agency tolerance of 0.1 ppm. Hessian fly has not been reported as an economic pest of wheat in California for the past 20 yr. Most Hessian fly puparia and pupa in our tests were located in wheat plants in the area below 1.9 cm above the bottom of the stem, an area below the cutting height of hay.