Impact of Fusarium graminearum on early-season soybean growth and seed yield under field conditions

Fusarium graminearum is primarily regarded as an economically important pathogen on wheat (Triticum aestivum L.) and corn (Zea mays L.), but recently it has also been shown to be pathogenic to soybean [Glycine max L. (Merr.)]. However, little is known about its impact on soybean early-season growth and seed yield under field conditions. A field experiment was conducted near Arlington, WI during the 2013 and 2014 growing seasons to quantify the effect of F. graminearum on soybean early-season growth and potential yield loss. The experiment was arranged as a randomized complete block with treatments in a 5 x 3 x 2 factorial design. Treatments consisted of five soybean cultivars, three seed treatments (non-treated control, mefenoxam + fludioxonil, and fluxapyroxad), and two inoculation treatments (non-inoculated and inoculated). Inoculating with F. graminearum did not significantly reduce soybean yield or above-ground and below-ground early-season growth measurements each year. The cultivar and seed treatment effects influenced early-season growth, but results were not consistent between years. The fungicide seed treatments used did not result in increased yield. Cultivar differences were the primary factor that affected soybean yield. Because there was no evidence that F. graminearum reduced early-season growth and seed yield under field conditions, the results from this study suggest soybean growers in Wisconsin should continue selecting the highest-yielding, best adapted cultivars for their region and making fungicide seed treatment decisions focusing on other pathogens.