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Seed treatment versus in-furrow fungicide effects on plant stand establishment and control of Rhizoctonia crown and root rot in sugar beet

Jason Brantner: University of Minnesota

<div><em>Rhizoctonia solani</em> is the most common sugar beet root pathogen in Minnesota and North Dakota, causing damping-off and Rhizoctonia crown and root rot (RCRR). In-furrow fungicides have been used but sometimes reduce emergence. New seed treatments are available that are more convenient for growers and safer during emergence. A field trial was conducted in <em>R. solani</em>-infested soil in 2016 and 2017 to compare four seed treatments and three in-furrow fungicides for stand establishment and control of <em>R. solani</em> in sugar beet. In 2016, the trial was replanted June 24 due to water damage. This late planting date resulted in warm soil temperatures and high disease pressure during stand establishment. In-furrow fungicides resulted in significantly (<em>P</em> = 0.05) higher plant stands at 4 weeks after planting, higher number of harvested roots, and lower severity and incidence of RCRR compared with seed-treatment fungicides. The 2017 trial was planted May 11 under cooler, drier soil conditions less favorable for emergence and disease. In-furrow fungicides resulted in significantly lower stand at 4 weeks after planting compared to seed treatments, but there were no significant differences in the number of harvested roots or RCRR ratings. Under high disease pressure, in-furrow fungicides provide better disease control than seed treatments, but environmental effects on both emergence and disease pressure influence the relative benefit.</div>