摘要
Three field experiments were conducted during 2016 and 2017 in southwestern Ontario, Canada to evaluate the effect of glyphosate/dicamba (2:1 ratio) applied at the V2/V3 or V4/V5 growth stage on dicamba-resistant (DR) soybean injury, growth response and yield. At 1 DAA, glyphosate/dicamba at 450, 900, 1350, 1800 and 3600 g·ae·ha-1 caused 0, 0.3, 1.8, 3.3 and 5.8% growth response (leaf droop) when applied at the V2/V3 growth stage and 0.3%, 1.3%, 1.5%, 2.3% and 4.5% growth response when applied at V4/V5 growth stage in DR soybean, respectively. The growth response was similar at 3 DAA. This response was transient with no growth response observed at 7 DAA, 2 WAB, 4 WAB, 8 WAB, and late Sept. (R8 growth stage). Glyphosate/dicamba at 450, 900, 1350, 1800 and 3600 g·ae·ha-1 caused 0.0, 1.4%, 3.6%, 5.7% and 10.7% injury (speckled chlorosis and necrosis and leaf distortion) when applied at the V2/V3 growth stage and 0.5%, 0.7%, 2.0%, 3.7% and 6.9% injury when applied at the V4/V5 growth stage in DR soybean, respectively. The injury observed was transient with no injury observed at 4 and 8 WAB and late Sept. (R8). There was no impact of glyphosate/dicamba at various rates evaluated on maturity and seed yield except at 1350 g·ae·ha-1 (V2/V3) and 3600 g·ae·ha-1 (V4/V5) which caused a 6% reduction in yield of DR soybean yield compared to the weed-free control. Based on these results, glyphosate/dicamba at the labelled rates can be safely applied at the V2/V3 and V4/V5 growth stage in DR soybean. However, care is needed to avoid spray overlaps as the 2× rate can result in significant crop injury and yield reduction in DR soybean.
Three field experiments were conducted during 2016 and 2017 in southwestern Ontario, Canada to evaluate the effect of glyphosate/dicamba (2:1 ratio) applied at the V2/V3 or V4/V5 growth stage on dicamba-resistant (DR) soybean injury, growth response and yield. At 1 DAA, glyphosate/dicamba at 450, 900, 1350, 1800 and 3600 g·ae·ha-1 caused 0, 0.3, 1.8, 3.3 and 5.8% growth response (leaf droop) when applied at the V2/V3 growth stage and 0.3%, 1.3%, 1.5%, 2.3% and 4.5% growth response when applied at V4/V5 growth stage in DR soybean, respectively. The growth response was similar at 3 DAA. This response was transient with no growth response observed at 7 DAA, 2 WAB, 4 WAB, 8 WAB, and late Sept. (R8 growth stage). Glyphosate/dicamba at 450, 900, 1350, 1800 and 3600 g·ae·ha-1 caused 0.0, 1.4%, 3.6%, 5.7% and 10.7% injury (speckled chlorosis and necrosis and leaf distortion) when applied at the V2/V3 growth stage and 0.5%, 0.7%, 2.0%, 3.7% and 6.9% injury when applied at the V4/V5 growth stage in DR soybean, respectively. The injury observed was transient with no injury observed at 4 and 8 WAB and late Sept. (R8). There was no impact of glyphosate/dicamba at various rates evaluated on maturity and seed yield except at 1350 g·ae·ha-1 (V2/V3) and 3600 g·ae·ha-1 (V4/V5) which caused a 6% reduction in yield of DR soybean yield compared to the weed-free control. Based on these results, glyphosate/dicamba at the labelled rates can be safely applied at the V2/V3 and V4/V5 growth stage in DR soybean. However, care is needed to avoid spray overlaps as the 2× rate can result in significant crop injury and yield reduction in DR soybean.
