Yuba R. Kandel, Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA 50011;
Carl A. Bradley, Department of Crop Sciences, University of Illinois, Urbana, IL 61801;
Kiersten A. Wise, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907-2054;
Martin I. Chilvers, Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824;
Albert U. Tenuta, Ontario Ministry of Agriculture and Food, Ridgetown, ON N0P2C0, Canada;
Vince M. Davis, Department of Agronomy, University of Wisconsin–Madison, WI 53706;
Paul D. Esker, School of Agronomy, University of Costa Rica, San Jose, CR;
Damon L. Smith, Department of Plant Pathology, University of Wisconsin–Madison; and
Mark A. Licht, Department of Agronomy, and
Daren S. Mueller, Department of Plant Pathology and Microbiology, Iowa State University, Ames
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Accepted for publication 15 August 2014.
Sudden death syndrome (SDS), caused by Fusarium virguliforme, is an important yield limiting disease of soybean. Glyphosate is used to control weeds in soybean; however, its effect on SDS is not clearly understood. The objective of this study was to examine the impact of glyphosate on SDS, yield, and plant nutrition under field conditions. Fourteen field experiments were conducted in Iowa, Illinois, Indiana, Michigan, Wisconsin, and Ontario, Canada during 2011 to 2013. The experiment consisted of six treatment combinations of glyphosate and herbicides not containing glyphosate. Disease index was significantly different across the location–years, ranging from 0 to 65. The highest disease was noted in locations with irrigation, indicating that high soil moisture favors development of SDS. There were no effects of herbicide treatments or interactions on disease. The foliar disease index among the treatments over all years ranged from 9 to 13. Glyphosate-treatments also tended to yield more than treatments of herbicides not containing glyphosate. There were no interactions between glyphosate-treatments and total manganese in plant tissue. The interaction of glyphosate with other nutrients in plant tissue was inconclusive. This 14 location–year study demonstrated that glyphosate application did not increase SDS severity or adversely affect soybean yield under field conditions.
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