Development of Fusarium head blight and accumulation of deoxynivalenol in barley sampled at different growth stages

Over the past six years (1993-1998), severe epidemics of Fusarium head blig ht (FHB), caused primarily by Fusarium graminearum, occurred on barley in t he Upper Midwest region of the United States. In addition to reducing the y ield and quality of barley, this pathogen also produces deoxynivalenol (DON ), a mycotoxin that can persist in malt and beer. In 1995 and 1996, a study was conducted to assess the development of FHB and the accumulation of DON in cv. Stander barley at the heading, early milk, late milk, soft dough, h ard dough, and mature developmental stages. In 1995, FHB severity increased markedly from the heading (0.7%) to soft dough (9.6%) developmental stages , and DON concentration increased from the heading (4.9 ppm) to late milk ( 36.8 ppm) stages. The increase in FHB and DON coincided with frequent and s ignificant precipitation. In 1996, the level of FHB was less than 1% up to the soft dough stage, after which it increased from 1.7% at the hard dough stage to 8.2% at maturity. DON concentrations were low and ranged from <0.2 to 0.7 ppm after the heading stage. These data indicate that FHB severity and possibly DON concentration can increase in barley at any time between t he heading stage and maturity.