Seed/seedling diseases of soybean caused Fusarium, Pythium, Phomopsis, Phytophthora, Macrophomina, Xylaria and Rhizoctonia have caused an estimated total economic loss of $17.6 billion in the U.S. between 1996 and 2016. As part of the proposed research, we are studying the biology of seedling pathogens, developing diagnostic tools, and using an integrated approach (seed treatments, cover crops, host resistance) to manage these organisms. In addition, we worked with Soybean Research & Information Network, submitted manuscripts, will present research updates scientific meetings (American Phytopathological Society), and updated the resources at the Crop Protection Network. These are our key findings: • Varieties containing Rps1c and Rps1k genes are no longer effective against Phytophthora sojae in the U.S. It may be important to consider varieties with Rps3a genes. (Paper published in a peer-reviewed journal and is made available to the community at large). • Parental materials with resistance to Fusarium graminearum are available for breeding programs to develop cultivars with disease resistance for farmers. (Paper published in a peer-reviewed journal and made available to the community at large). • Planting of rye cover crop contributes to soybean taproot decline disease progression caused by Xylaria necrophora • A diagnostic assay has been developed to detect the tap root decline pathogen Xylaria necrophora in soybean samples and this will be made available to diagnosticians in plant disease clinics to diagnose farmer samples. • Preliminary studies indicate that corn stubble can influence the soil population number of Fusarium in the soil, when compared to fallow. • A diagnostic assay has also been developed to detect multiple root rot pathogens, species of Fusarium and Rhizoctonia solani in soybean samples and this will be made available to diagnosticians in plant disease clinics to diagnose farmer samples. (Paper published in a peer-reviewed journal and made available to the community at large). • Biochar soil amendments have been demonstrated to significantly reduce root rot caused by Fusarium graminearum and Pythium sylvaticum in lab conditions, however further evaluations need to be performed (for e.g., in the greenhouse). • Certain fungicides have been demonstrated to be effective against seed pathogens. For example, QoIs tend to control Phomopsis seed infection and DMIs have a better control of purple seed stain when compared to the non-treated control. • Certain seed treatment products such as CeraMax, ILEVO and Saltro have been demonstrated to be effective against Rhizoctonia solani. Three weeks after planting, the number of emerged plants was significantly greater for products compared to those in the non-treated control plots. • The 2023 soybean seed treatment efficacy guide with updated ratings. Link - https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-soybean-seedling-diseases (# of Downloads from CPN website 2/24/23-10/17/23: 916).

• New information is available on varieties with Rps3a genes that should be considered for the management of Phytophthora in soybeans. • New information on varieties with resistance to Fusarium graminearum is made available for breeding programs so that commercial-resistant cultivars can be developed. • Use of cover crops can lead to an increased severity of soybean diseases such as taproot decline. Currently, we have limited information on taproot decline, and research on pathogen biology provides us with information to develop disease management strategies. • Currently, we have limited information on taproot decline, and research on developing appropriate disease diagnostic tools helps us help farmers identify the disease accurately and develop disease management strategies. • The use of rotational crops (such as corn) can lead to an increased severity of soybean diseases such as those caused by Fusarium. Currently, we have limited information on the management of Fusarium diseases, and research on pathogen biology provides us with information to develop alternative disease management strategies (such as cultural practices). • The use of biochar soil amendments is less known in their effectiveness against Fusarium and Pythium. Thus, research on biochar soil amendments can provide us with information to develop alternative disease management strategies (that is besides the use of fungicides and resistant cultivars). • The use of foliar fungicides against seed pathogens is not known. In years when the weather conditions are wet, and pathogens such as Diaporthe and Cercospora could be problematic, this information will help us provide recommendations to farmers to minimize the risk of infection of soybean seeds by such pathogens. • Seed treatment products are commonly used against organisms such as Fusarium virguliforme which causes soybean sudden death syndrome. The research question was if we use these products against one fungus, can we control the same product against another fungus, what we are finding is that the same products can be effective against Rhizoctonia solani, and the farmers do not have to add additional active ingredients to control a second pathogen. • The group brings out the seed treatment efficacy guide every year to help farmers decide what product is best for their field. Root rot pathogens are complex meaning there are several fungi and other organisms that can compromise soybean growth early in the season. Considering the revenue invested by soybean farmers to manage seedling diseases, we find such efficacy charts beneficial for farmers and allow them to maximize their return on investment.