Developing Management Strategies for Taproot Decline, Xylaria sp., in Soybean

Soybean (Glycine max) is one of the most important oilseed crops in the world. Taproot decline is a recently discovered disease caused by Xylaria sp., a novel species located within the Xylaria arbuscula aggregate. Foliar symptoms include interveinal chlorosis and necrosis, and upon further investigation, there are often dead plants adjacent within the row. Many other soybean diseases have similar foliar symptoms; therefore, more examination is usually required for proper identification. Soybean debris from previous years is suspected to be the primary source of inoculum. Plants may be infected at any point during the growing season, often resulting in premature death. Precision planting, reduced tillage, and soybean monoculture may contribute to disease incidence and severity. There is little knowledge of genetic resistance, fungicide efficacy, or cultural practices that may be useful in managing taproot decline. In greenhouse trials we have identified susceptible, moderately susceptible, moderately resistant, and resistant soybean varieties for growers. Limited field data appears to corroborate these results, and more research is needed. To date, no promising seed treatments have been identified in the field. However, a few promising in-furrow fungicide treatments have been identified in field trials. Results from on-farm studies indicate that taproot decline causes significant yield loss. Results from these projects will directly benefit Louisiana stakeholders by providing potential management options for taproot decline.