Effect of Glyphosate Application on Sudden Death Syndrome of Glyphosate-Resistant Soybean Under Field Conditions

Abstract

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.

Lack of transgene and glyphosate effects on yield, and mineral and amino acid content of glyphosate‐resistant soybean

“…We found no effects of any of the variables studied on yield. This is in line with previous studies which found no negative effect of glyphosate or the GR transgene on yield of GR soybean . The most extensive set of studies on the effects of glyphosate on yield of GR soybean was published in 1995, the year before this GR crop was first grown commercially by farmers .…”

“…This study evaluated the effects at 17–23 locations over 3 years and found no effect on yield. Kandel et al . reported at some locations glyphosate‐treated GR soybean had significantly greater yields than GR soybean in which herbicides other than glyphosate were used for weed management.…”

“…Although yields of cotton, maize and soybean in the USA have continued upward since these GR crops were introduced, some have claimed that glyphosate causes deficiencies in cationic minerals in GR crops, due to either the chelation of glyphosate with divalent metal cations and/or toxic effects on rhizosphere microbes involved in the assimilation of these nutrients from soil . Others have found no effects of glyphosate on mineral content in GR crops . In a review of most of this literature, the authors concluded that the strongest available evidence in the literature supported the view that glyphosate does not significantly affect mineral nutrition in GR crops.…”

“…[4][5][6][7][8][9][10][11][12][13][14][15] Others have found no effects of glyphosate on mineral content in GR crops. [16][17][18][19][20][21][22][23][24][25][26][27] In a review of most of this literature, 2 the authors concluded that the strongest available evidence in the literature supported the view that glyphosate does not significantly affect mineral nutrition in GR crops. However, the authors stated that there might be effects with particular soil types, crop cultivars, glyphosate formulations and/or environmental conditions.…”

How glyphosate affects plant disease development: it is more than enhanced susceptibility

“…Similar results were reported by Njiti et al 52 A recent multi-year study conducted across several US states and one Canadian province provided further evidence that neither the glyphosate resistance trait nor application of glyphosate to these soybean lines had any impact on the severity of sudden death syndrome. 53…”