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Summary: Sudden death syndrome (SDS), caused by Fusarium virguliforme, is an economically important disease of soybean. Glyphosate use in soybean to control weeds has been increased significantly after the discovery of glyphosate resistant soybeans. Glyphosate has been reported to stimulate the growth of fungi and enhances the virulence of the pathogen, weaken the soybean plant, make nutrients, which are important for defense, unavailable making it more susceptible to organisms that cause disease. However, its effect on SDS is not clearly understood. A limited studies carried out in late 1990s did show inconsistent results. In 2011 -2013, a total of 14 field experiments were conducted to investigate the impact of glyphosate on SDS, yield, and plant nutrition. Field experiments were conducted in Iowa, Illinois, Indiana, Michigan, Wisconsin and Ontario, Canada. Six combinations of herbicides with and without glyphosate were compared. Experiments were conducted in field with history of SDS. Some locations were also inoculated with F. virguliforme local isolates and irrigated to create conducive environment for the disease. Disease, yield and nutrient content in plant tissue data were collected. Disease index was significantly different across the location-years. The highest disease was noted in locations with irrigation indicating high soil moisture favor development of SDS. There were no effects of herbicide treatments or interactions on disease. The FDX among the treatments over all site-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 fourteen location-year study demonstrated that glyphosate application did not increase SDS severity or adversely affect soybean yield under field conditions.
United Soybean Board (USB) farmer-leaders develop and maintain partnerships with U.S. land grant universities and U.S. ag-focused research organizations such as the Plant Management Network to increase the transfer of checkoff-funded applied and practical production research information to U.S. soybean farmers. USB neither recommends nor discourages the implementation of any advice contained herein, and is not liable for the use or misuse of the information provided.