COMPLETE MORTALITY OF HESSIAN FLY (DIPTERA, CECIDOMYIIDAE) PUPARIA IN2 LARGE-SCALE TESTS TO CONFIRM THE EFFICACY OF A MULTIPLE QUARANTINE TREATMENT FOR COMPRESSED HAY EXPORTED TO JAPAN

Hessian By, Mayetiola destructor (Say), was reared in a greenhouse in Fresno, CA, to eliminate interstate shipments of test materials. Two l arge-scale tests fulfilled regulatory test requirements for control of Hessian By in compressed hay for export to Japan. We confirmed the ef ficacy of a multiple quarantine treatment (greater than or equal to 80 kg/cm(2) compression and 60 g/28.3 m(3) aluminum phosphide for 7 d at 22 degrees C). A large-scale test with timothy, Phleum pratense, hay and a 2nd test with alfalfa, Medicago sativa, combined with Sudan gras s, Sorghum bicolor sudanensis, hays loaded in 76.2-m(3) freight contai ners resulted in complete mortality of 38,957 and 37,345 Hessian fly p uparia, respectively. These species of hay were representative of prev iously tested species including oat, Avena sativa, and Bermuda grass, Cynodon dactylon, hays and rye straw, Secale cereale. Copper plate cor rosion values, bale temperatures, and fumigant concentrations were sim ilar throughout the freight containers in both tests. Lower fumigant c oncentrations in the 2nd test than in the 1st test were attributed to leakage. Hydrogen phosphide residues 1 d after fumigation and overnigh t aeration resulted in concentrations below the U.S. Environmental Pro tection 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 H essian 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 t he cutting height of hay.