Twelve field trials (five with PRE and seven with POST herbicides) were conducted over a 4-yr period (2006Á2009) on various Ontario farms with heavy giant ragweed infestations (22 plants m (2) to determine the effectiveness of preemergence (PRE) and postemergence (POST) herbicides for the control of giant ragweed in corn. Atrazine, dicamba, dicamba/atrazine, isoxaflutole plus atrazine, mesotrione plus atrazine, saflufenacil, and saflufenacil/dimethenamid applied PRE provided 9Á52, 60Á80, 64Á83, 44Á77, 33Á80, 36Á80, and 43Á63% control of giant ragweed, reduced giant ragweed

Soltani, N., Nurse, R. E., Robinson, R. E. and Sikkema, P. H. 2011. Effect of ammonium sulfate and water hardness on glyphosate and glufosinate activity in corn. Can. J. Plant Sci. 91: 1053–1059. Eight field trials were conducted over a 3-yr period (2008 to 2010) near Harrow and Ridgetown, Ontario, to evaluate the effect of water hardness (distilled: 0 ppm; intermediate: 353 ppm; and very hard 1799 ppm) on full label doses of glyphosate (900 g a.e. ha−1) and glufosinate (400 g a.i. ha−1) [with and without ammonium sulfate (AMS) at 2.5 L ha−1] efficacy in corn. There was no effect of water hardness on control of velvetleaf (ABUTH), redroot pigweed (AMARE), common lambsquarters (CHEAL), and annual grasses green foxtail (SETVI) and barnyardgrass (ECHCG) when glyphosate was applied with or without the AMS. There was also no difference in yield of corn with various water sources when glyphosate was applied with or without AMS. Glyphosate applied with various water sources with or without AMS controlled ABUTH, AMARE, CHEAL, and annual grasses better than glufosinate with or without AMS. Glufosinate with AMS, especially at the 1799 ppm water hardness, generally controlled ABUTH, AMARE, and CHEAL better than glufosinate without AMS, but there was no improvement in annual grass control. Contrasts indicated an 11% increase in yield when glufosinate was applied with AMS compared with when applied without AMS. Based on these results water hardness and AMS had little benefit on the efficacy of glyphosate in corn; however, efficacy of glufosinate was improved when applied with AMS at high water hardness.

No abstract

Soltani, N., Shropshire, C. and Sikkema, P. H. 2011. Short Communication: Influence of manganese on efficacy of glyphosate in glyphosate-resistant soybean. Can. J. Plant Sci. 91: 1061–1064. Four field trials were conducted from 2007 to 2010 in Ontario to evaluate the effect of various manganese (Mn) formulations (Mn1, Ecoman 5% Mn; Mn2, MangaMax 5.5% Mn; Mn3, ManMax 5.5% Mn; Mn4, Superman 5% Mn; Mn5, Stoller This 5% Mn; Mn6, Nortrace 6% Mn-EDTA (ethylenediaminetetraacetate); Mn7, Nortrace 22% Mn and Mn8, WolfTrax 33% Mn) applied at 2.0 kg actual Mn ha−1 on glyphosate efficacy at 900 g a.e. ha−1 in glyphosate-resistant soybean. The tank mix of glyphosate plus Mn4, Mn6 or Mn8 caused as much as 6, 17 and 4% injury in soybean, respectively. There was minimal crop injury (0–1.4%) with other Mn tank mixes. The addition of Mn4 or Mn6 to glyphosate did not antagonize glyphosate efficacy on the weeds evaluated (AMARE, AMBEL, CHEAL and SETVI). The other Mn formulations antagonized glyphosate efficacy for the control of AMARE, AMBEL, CHEAL or SETVI under some environments. The addition of Mn3 or Mn6 to glyphosate reduced soybean yield as much as 15 and 10% compared with glyphosate alone, respectively. Based on these results, it is recommended that glyphosate and manganese applications be applied sequentially to avoid weed control antagonism and maximize soybean yield.