Lynette R. Brown, Nader Soltani* , Christy Shropshire and Peter H. Sikkema
Two sets of experiments were conducted over a four-year period (2006-2009) to evaluate the tolerance of winter wheat to fall applications of 2 week preplant (WPP), 1 WPP, 1 day preplant (DPP) and preemergence (PRE) glyphosate tankmixes in combination with commonly used burndown herbicides (amitrole, dicamba/diflufenzopyr, chlorimuron-ethyl, dicamba, 2,4-D amine and 2,4-D ester). Glyphosate plus 2,4-D amine, 2,4-D ester or amitrole tankmixes applied 2 and 1 WPP, 1 DPP and PRE caused minimal wheat injury and no yield decrease. Glyphosate plus dicamba applied 1 DPP and PRE caused 3.6 and 6.4% injury shortly after emergence, however, this injury was transient and did not affect final yield. Glyphosate plus dicamba/diflufenzopyr applied 1 DPP and PRE caused less than 5% injury in Exeter and up to 27% in Ridgetown which resulted in a yield loss of 1.1 t ha-1 at 1 DPP. The glyphosate plus chlorimuron-ethyl tankmix caused the most injury at all four application timings. Injury with this tankmix was evident 2 weeks after emergence and by July of the following year was as high as 54%. This tankmix caused a decrease in height of 4 to 7 cm and a yield loss of 0.7-3.1 t ha-1 .
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