Effects of field-applied fungicides, grain moisture, and time on deoxynivalenol during postharvest storage of winter wheat grain

Fusarium head blight, caused mainly by Fusarium graminearum Schwabe, results in major losses in wheat. In two separate field experiments, spikes of winter wheat cultivars ‘Overland’ (moderately resistant) and ‘Overley’ (susceptible) were sprayed at anthesis with the triazole fungicide Prosaro (prothioconazole + tebuconazole) or the strobilurin fungicide Headline (pyraclostrobin) or not sprayed. Following harvest, deoxynivalenol (DON) concentrations were monitored during 120 d of grain storage at 10 °C, 40% relative humidity, and 10%, 16%, or 20% grain moisture. In ‘Overland’, DON decreased significantly at P = 0.05 from an average of 3.6 to 3.0 μg g −1 in the check and decreased from 2.7 to 2.2 μg g −1 in the Prosaro treatment. DON did not significantly decrease (4.4–4.1 μg g −1 ) in the Headline treatment. DON concentrations did not differ between 16% (3.1 μg g −1 ) and 20% (3.0 μg g −1 ) grain moisture. In ‘Overley’, DON increased significantly from 3.1 to 3.6 μg g −1 in the check and from 2.9 to 3.5 μg g −1 in the Headline treatment, but remained the same at 2.2 μg g −1 in the Prosaro treatment. DON concentrations were not different between 16% (3.2 μg g −1 ) and 20% (3.1 μg g −1 ) grain moisture but were significantly lower (2.7 μg g −1 ) at 10% grain moisture. These results indicate that the effects of fungicides applied at anthesis in the field can impact DON concentrations through grain storage. Triazoles are recommended over strobilurins to achieve this extended postharvest protection from DON, and grain moisture during storage should be below the maximum safe level of 13.5% at 10 °C.