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Efficacy of fluopyram seed treatment in management against Fusarium brasiliense, a new dry bean root rot pathogen in Michigan

Kjersten Oudman: Michigan State University

<div><em>Fusarium</em> root rot of dry bean is caused by several species in Michigan. According to a dry bean <em>Fusarium</em> root rot survey conducted in Michigan from 2014 to 2017, the most common species are within the <em>Fusarium solani</em> species complex (FSSC) clade 2, such as <em>F. cuneirostrum</em> and <em>F. phaseoli</em>. However, a new species to North America was also isolated from dry beans in high abundance: <em>F. brasiliense (unpublished data)</em>. <em>F. brasiliense</em> is endemic to South America and is known to be a causal agent of soybean sudden death syndrome (SDS) despite being isolated from many dry beans in Michigan. <em>F. virguliforme</em>, a SDS pathogen of the same clade, is another prevalent species in Michigan on soybeans. As soybeans and dry beans are often grown in the same locations in Michigan and both<i> F. virguliforme </i>and<i> F. brasiliense</i> are widespread in these areas, it is necessary to understand the impact of these two species on dry beans. An inoculated field trial was set up in the summer of 2017 to test the aggressiveness of <em>F. brasiliense </em>and<em> F. virguliforme</em> on two dry bean cultivars and the efficacy of fluopyram (ILeVO; Bayer CropScience) seed treatment. <em>F. brasiliense</em> significantly decreased shoot mass and increased root rot ratings. However, fluopyram seed treatment significantly decreased root rot ratings in the inoculated plants, a finding complimented by quantitative PCR assays that revealed significantly decreased pathogen presence in roots treated with the fluopyram seed treatment as compared to the non-treated controls. <em>F. brasiliense</em> is a new concern for dry bean growers, however fluopyram has potential to control this pathogen.</div>