Late-Season Grass Weed Management with In-Crop and Post-Harvest Herbicides in Twin-Row Glyphosate-Resistant Soybean


Emergence of grasses late in the season has become a problem in glyphosate-resistant (GR) soybean production in the southern US. A 3-yr field study was conducted from 2011 to 2013 at Stoneville, MS to determine efficacy of post-harvest and pyroxasulfone-based in-crop herbicides on late-season grasses and yield in twin-row glyphosate-resistant soybean. Experiments were conducted in a split-plot arrangement of treatments in a randomized complete block design with fall herbicides (with and without pendimethalin at 1.12 kg ai ha-1 and paraquatat 0.84 kg ai ha-1) as main plots and in-crop herbicides as subplots with four replications. The six in-crop herbicide programs were: glyphosate applied early postemergence (EPOST) at 0.84 kg·aeha-1 followed by (fb) glyphosate late postemergence (LPOST) at 0.84 kg·ha-1 with and without pyroxasulfone preemergence (PRE) applied at 0.18 kg ai ha-1, pyroxasulfone PRE fb glyphosate at 0.84 kg·ha-1 LPOST or glyphosate at 0.84 kg·ha-1 + S-metolachlor at 1.68 kg ai ha-1 EPOST, pyroxasulfone PRE fb S-meto- lachlor at 1.12 kg·ha-1 + fomesafen at 0.27 kg ai ha-1 EPOST fb clethodim at 0.14 kg ai ha-1, and a no-herbicide control. Browntop millet, Digitaria spp., and junglerice densities at 2 weeks after LPOST, grass weed dry biomass at harvest, and soybean yield were similar regardless of post- harvest herbicides in all three years. At 2 weeks after LPOST, browntop millet, Digitaria spp. and junglerice densities were greatly reduced in all five in-crop herbicide treatments compared with no herbicide plot in all three years. Grass weed dry biomass in no-herbicide plots was 3346, 6136, and 6916 kg·ha-1 in 2011, 2012, and 2013, respectively and the five herbicide treatments reduced grass weed dry biomass by at least 87%, 84%, and 99% in 2011, 2012, and 2013, respectively. Soybean yield was higher with all five in-crop herbicide treatments compared to no herbicide control in all three years. These results indicate that browntop millet, Digitaria spp., and junglerice infestations can be reduced with pyroxasulfone-based in-crop herbicide programs in twin-row GR soybean.

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Reddy, K. , Bryson, C. and Nandula, V. (2015) Late-Season Grass Weed Management with In-Crop and Post-Harvest Herbicides in Twin-Row Glyphosate-Resistant Soybean. American Journal of Plant Sciences, 6, 213-218. doi: 10.4236/ajps.2015.61024.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Duke, S.O. (2011) Glyphosate Degradation in Glyphosate-Resistant and -Susceptible Crops and Weeds. Journal of Agricultural and Food Chemistry, 59, 5835-5841.
[2] Reddy, K.N. and Norsworthy, J.K. (2010) Glyphosate-Resistant Crop Production Systems: Impact on Weed Species Shifts. In: Nandula, V.K., Ed., Glyphosate Resistance in Crops and Weeds: History, Development, and Management, John Wiley & Sons, Inc., Hoboken, 165-184.
[3] Reddy, K.N. and Nandula, V.K. (2012) Herbicide Resistant Crops: History, Development and Current Technologies. Indian Journal of Agronomy, 57, 1-7.
[4] Reddy, K.N. and Bryson, C.T. (2009) In-Crop and Autumn-Applied Glyphosate Reduced Purple Nutsedge (Cyperus rotundus) Density in No-Till Glyphosate-Resistant Corn and Soybean. Weed Technology, 23, 384-390.
[5] (2014) Pyroxasulfone. In: Shaner, D.L., Ed., Herbicide Handbook, Weed Science Society of America, Lawrence, Kansas, 395-396.
[6] Kurtz, M.E., Yamaji, Y. and Deloach, Y.T. (2009) KIH-485 (Pyroxasulfone): Broadleaf Signalgrass (Urochloa platyphylla) Control with Early Pre-Plant Applications in Minimum and Conventional Tillage Corn. Proceedings of Southern Weed Science Society, 62, 327.
[7] Porpiglia, P.J., Nakatani, M. and Ueno, R. (2005) KIH-485: A New Broadspectrum Herbicide. Weed Science Society of America Abstracts, 45, 314.
[8] Walsh, M.J., Fowler, T.M., Crowe, B., Ambe, T. and Powles, S.B. (2011) The Potential for Pyroxasulfone to Selectively Control Resistant and Susceptible Rigid Ryegrass (Lolium rigidum) Biotypes in Australian Grain Crop Production Systems. Weed Technology, 25, 30-37.
[9] Watanabe, O., Porpiglia, P.J., Yamaji, Y. and Honda, H. (2006) Residual Control with KIH-485. Weed Science Society of America Abstracts, 46, 13.
[10] Mueller, T.C. and Steckel, L.E. (2011) Efficacy and Dissipation of Pyroxasulfone and Three Chloroacetamides in a Tennessee Field Soil. Weed Science, 59, 574-579.
[11] Reddy, K.N. and Boykin, J.C. (2010) Weed Control and Yield Comparisons of Twin- and Single-Row Glyphosate-Resistant Cotton Production Systems. Weed Technology, 24, 95-101.

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