Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
Sudden Death Syndrome (SDS) is an important disease that impacts soybean growers in the Mid-Atlantic. The disease is caused by a fungus that infects seedling roots early in the season. After flowering, and when conditions are warm and wet, interveinal necrosis, defoliation, and plant death can occur. For more information on SDS see my article from August 30th.
It has been suggested by some that glyphosate use can exacerbate diseases of field crops. Some suggest manganese may play a role in these putative effects. A recent publication in the journal Plant Disease examined the effects of glyphosate on SDS, yield, and plant nutrition. A total of 14 field experiments were conducted in the Midwest and parts of Canada from 2011 through 2013. What did they find?
1) There were no effects of glyphosate or herbicide use on SDS
2) Glyphosate use tended to be associated with increased yields
3) Glyphosate did not impact plant manganese levels
4) SDS was worse in irrigated fields
In sum, these data indicate that glyphosate use is not likely to increase SDS or alter manganese levels in plant tissues. Glyphosate use does suppress weeds and increase yields. If you have a field with a history of SDS, avoid over-irrigation, which favors infection and disease development.
Reference: Kandal et al. 2014. Effect of glyphosate application on sudden death syndrome of glyphosphate-resistant soybean under field conditions. Plant Disease. http://dx.doi.org/10.1094/PDIS-06-14-0577-RE