Session 2: Fhb Management

Knowledge of the relative contribution of within-fi eld inoculum sources of Gibberella zeae to infection of local wheat and barley is important for developing and/or excluding strategies for managing FHB. Our experimental objective was to quantify the relative contribution of within-fi eld corn debris as an inoculum source of Gibberella zeae for Fusarium head blight and DON contamination in ten variable wheat environments in 2009, all in regions where corn is the predominant crop in the agricultural landscape and corn debris is left on the land surface over large areas. Our research is based on the hypothesis that spores of Gibberella zeae that are deposited on wheat spikes and that result in Fusarium head blight come primarily from well-mixed, atmospheric populations in an area. The research was conducted in two commercial-scale wheat fi elds in Illinois, Missouri, Nebraska, New York, and Virginia, each following an FHB nonsusceptible crop. Over these environments we encountered six severe epidemics (in Illinois, Missouri, and Virginia), two moderate epidemics (in New York), and two mild epidemics (in Nebraska). Locally overwintered, natural corn stalks were collected in spring from two different sources in each state or locale by placing a 33 inch diameter plastic ‘Hoola Hoop’ onto four arbitrarily selected areas in a corn stubble fi eld, and then removing all of the stubble within the hoop and placing it in a paper bag. Replicated (four) microplots containing corn debris and without debris were set out in each fi eld and were separated by a minimum of 100 ft in each dimension. Debris was secured within the source circles by using cages fashioned of 2 ft high hardware cloth and shaped with the same 33 inch diameter plastic ‘Hula Hoop’, fastened with plastic zip-ties, and secured to the soil with metal ground staples. Wheat heads above each microplot were rated at soft dough stage for FHB incidence, severity, and index. At grain maturity, at least 100 heads from each microplot were harvested, dried and shipped to Cornell where grain was threshed from a subsample of heads and sent to Virginia Tech for DON analysis. Only in one fi eld in Virginia did wheat heads from microplots containing locally overwintered corn debris show a slight but statistically signifi cant increase in FHB incidence and index over those from microplots with no corn debris. The astounding result is that DON level did not differ signifi cantly between corn debris and no debris microplots in any of the ten wheat environments. By inference of our results, it appears that elimination of corn debris from single wheat fi elds in a major corn producing region may have rather limited benefi ts in terms of reducing FHB and especially of reducing DON contamination of grain. The experiments will be repeated in ten additional environments in 2010. ACKNOWLEDGEMENT AND DISCLAIMER This material is based upon work supported in part by the U.S. Department of Agriculture under agreement No. 59-070-4-093. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, fi ndings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily refl ect the view of the U.S. Department of Agriculture.