Effect of post-anthesis fungicide applications to manage fusarium head blight in winter wheat

Fusarium head blight (FHB) of wheat, caused by the fungus Fusarium graminearum, is currently considered one of the most economically important diseases on wheat in the North Central United States. The fungus causes light-weight tombstone grains to form and produces the mycotoxin deoxynivalenol (DON), reducing the yield and quality of the grain. Currently, farmers rely heavily on the sterol demethylase Inhibitor (DMI) triazole fungicide Prosaro (Bayer CropScience) to protect their crop from this disease. The optimal fungicide application timing is traditionally believed to be early anthesis - Feekes Growth Stage (FGS) 10.5.1. However, environmental conditions and uneven flowering across a field at this growth stage can hinder precise fungicide application. Field trials were conducted at the Agronomy Center for Research and Education in West Lafayette, IN in the 2012-2013 and 2013-2014 growing seasons to determine the impact of post-anthesis fungicide timing in conjunction with initial infection by F. graminearum and subsequent development of FHB and DON. Treatments consisted of single applications of Prosaro at 475 mL/ha applied at Feekes Growth Stage 10.5.1 (anthesis), and anthesis + 1, 3, 5, 7, 9, and 11 days. In 2013 all plots were inoculated with macroconidia of F. graminearum and non-treated inoculated plots served as controls. In 2014, an additional treatment was included that did not receive inocula or fungicide. Disease index was assessed ten days after the final treatment. DON and yield were evaluated post-harvest. Results indicate that fungicide applications made up to 11 days post-anthesis may be useful in reducing FHB and DON when conditions are favorable for disease development. Fungicide application had a significant effect on DON ( P \u3c 0.0001) in both 2013 and 2014. Mean DON values were numerically lower at every application time in both years compared to the non-fungicide treated control. These results indicate that fungicide application after anthesis may be useful in reducing FHB and mycotoxin levels in wheat