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 blight (FHB), caused primarily by Fusarium graminearum, occurred on barley in the Upper Midwest region of the United States. In addition to reducing the yield 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, hard 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 significant 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 HB severity and possibly DON concentration can increase in barley at any time between the heading stage and maturity.