Field testing of antagonists of Fusarium head blight incited by Gibberella zeae

Fusarium head blight (FHB), primarily caused by Gibberella zeae (anamorph=Fusarium graminearum), is a devastating disease that causes extensive yield and quality losses to wheat and barley throughout the world. Antagonists that suppressed FHB in earlier greenhouse studies were tested in a series of field experiments at different geographical locations in the United States in 1998–2000. In most cases, the yeasts Cryptococcus nodaensis OH182.9, Cryptococcus sp. OH 71.4, and Cryptococcus sp. OH 181.1 decreased disease severity throughout the study at all locations. The most effective antagonists reduced disease severity by as much as 50–60%. The efficacy of some antagonists differed depending on the dose applied, but differences were not necessarily related to a dose–response. Antagonist biomass produced in two liquid culture media with differing carbon to nitrogen (C:N) ratios suppressed FHB disease severity. On the susceptible winter wheat cultivar Pioneer 2545 at Peoria, IL, in 2000, yeast OH 182.9 reduced disease severity by 60% and by 45%, compared to the buffer control when produced in C:N 11.0 and 6.5 medium, respectively. The influence of C:N ratio of the production medium on antagonist efficacy on cultivar Pioneer 2545 varied with the antagonist considered but did not influence disease reduction on the moderately resistant winter wheat cultivar Freedom at the Peoria, IL or Wooster, OH, locations. The lowest levels of disease of any study occurred when antagonists were applied to this moderately resistant cultivar. Biological control of FHB offers a potentially useful tool for inclusion in an IPM program for combating FHB on winter and spring wheats.