Corn residue is a significant source of inoculum for epidemics of Fusarium head blight (FHB) in wheat and barley, but little is known about the influence of different amounts of corn residue on FHB. We monitored the spread of a released clone of Gibberella zeae (Fusarium graminearum), causal agent of FHB, from small 0.84-m-diameter research plots containing 45, 200, or 410 g of infested corn stalk pieces in winter wheat and barley fields in Virginia over 3 years (2008 to 2010). The fungus was recaptured through the collection of wheat and barley spikes at 0 and 3 m from the source and the released clone was identified in heterogeneous background populations using amplified fragment length polymorphisms. Results showed a slightly greater intensity of recovery of the clone at a greater distance when more infested residue was present. Plots containing larger amounts of inoculum (410 g) generally resulted in a smaller decline of recovery of the clone at 3 m from the source, indicating a greater spread from the larger inoculum source. The clone was also recovered at distances ≥18 m from inoculum sources. Larger amounts of corn residue generally had less influence on clone recovery in plots containing a moderately resistant wheat cultivar than those containing a susceptible wheat cultivar.
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