Session 1: Fhb Management

Fusarium head blight (FHB) is a serious disease of wheat. The best controls for FHB are planting of resistant cultivars and application of fungicides to heads. However integrating these strategies may provide additional benefits for small grain producers including reduced disease losses and lower levels of the toxin deoxynivalenol (DON). This research was conducted to determine if resistant cultivars show higher benefits (greater reductions in DON) from fungicide application than susceptible ones. A winter wheat field experiment was established and infested with corn grains colonized by Fusarium graminearum applied to the soil surface in three applications about 2 wk apart beginning 4 wk prior to heading (100 g/m2 total applied). During heading and flowering, plots were sprinkler irrigated (3 min/hr) from 9:00 p.m. until 6:00 a.m. Six winter wheat cultivars were selected based upon their reaction to FHB on a 1-9 scale where 1=resistant and 9=susceptible. The six cultivars, followed by their reactions, were Truman (3), Heyne (4), Roane (5), Karl 92 (6), Overley (9), and Tomahawk (9) and were arranged in a split-plot design with cultivars as main plots and presence or absence of fungicide as sub-plots. There were four replications and sub-plots were 5’ by 15’. The fungicide Prosaro (6.5 fl oz/A plus Induce spreader at 0.125%) was applied at the fully headed growth stage using flat-fan nozzles angled forward about 30°. FHB index (% blighted florets) was determined for each sub-plot on May 30, June 2, June 4, and June 9. Sub-plots were harvested with a small-plot combine to determine yields and percentage Fusarium-damaged kernels (FDK). Ground grain samples were sent to the North Dakota State University Veterinary Diagnostic lab for analysis of DON). Severe FHB developed at the site as evidenced by the nonsprayed susceptible cultivar Tomahawk yielding only 7.9 bu/A; however, the non-sprayed moderately resistant cultivar Truman yielded 56.2 bu/A, so yield potential at the site was good. There were significant (P=0.0133, 0.0041, 0.0002, respectively) correlations between grain yields, average FHB index, and FDK and the reduction in DON achieved by fungicide application. These correlations indicate that a cultivar’s resistance reaction to FHB can help predict the degree of DON reduction by the fungicide Prosaro. More resistant cultivars show higher reductions. Although there were significant correlations between DON reductions from fungicide and three resistance parameters (yields, disease index, FDK), the R2 values indicate that a cultivar’s resistance reaction to FHB explained only 26-48% of the reduction. Clearly, there are other factors that influence DON reduction from fungicide application. However, if these findings are confirmed for naturally occurring FHB epidemics, it may be possible to reduce the impact of the disease and toxin in Kansas by combining fungicides with more resistant cultivars.