Field experiments in 2013 and 2014 examined corn (Zea mays L.) tolerance to acetyl-coenzyme A car... more Field experiments in 2013 and 2014 examined corn (Zea mays L.) tolerance to acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides in a scenario where they would have been used to terminate a failed corn stand prior to replanting. To simulate this, herbicides were applied 1 wk or 1 d preplant (PP) and several parameters were measured. Corn injury 1, 2, 4, or 8 wk after emergence (WAE) was similar to the untreated control, regardless of herbicide, rate, or PP application timing. Across herbicides and rates, PP timing did not affect plant stand and aboveground biomass 2 WAE, plant height 4 WAE, or yield. Across application timings, plant stand and aboveground biomass were similar to the untreated control, regardless of herbicide treatment or rate; however, some herbicides reduced height and (or) yield. For example, compared with the untreated control, fluazifop-p-butyl (75 and 150 g ha−1) and sethoxydim (300 g ha−1) each reduced height by about 3%, while clethodim (30 and 60 g h...
Abstract: Populations of glyphosate-resistant (GR) Canada fleabane and GR giant ragweed can be fo... more Abstract: Populations of glyphosate-resistant (GR) Canada fleabane and GR giant ragweed can be found in several locations in southwestern Ontario. While these species can be managed individually, a scenario has developed where both species are present in GR soybean. Ten separate field experiments (five with Canada fleabane and five with giant ragweed) were conducted over a 2-yr period (2013-2014) in soybean to evaluate preplant (PP) herbicide tank mixtures that could control both weed species if they were present in the same field. Herbicides were rated for soybean injury, weed control, population density, and aboveground biomass. Two- and three-way tank mixtures containing amitrole (i.e., glyphosate + amitrole, glyphosate + amitrole + saflufenacil, and glyphosate + amitrole + 2,4-D) were among the most effective treatments. For example, control of GR Canada fleabane and GR giant ragweed was at least 92% at 4 wk after treatment (WAT) and weed density and biomass were generally similar to the weed-free control. However, without amitrole, the best PP herbicide option was a three-way tank mixture of glyphosate + saflufenacil + 2,4-D which provided improved control and greater reductions in density and biomass compared with the two-way glyphosate tank mixtures containing saflufenacil or 2,4-D.
Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitativ... more Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitative data regarding its pattern and mechanisms of spread in crop fields are lacking. To address this gap, we conducted a Web-based survey of certified crop advisors in the U.S. Corn Belt and Ontario, Canada. Participants were asked questions regarding giant ragweed and crop production practices for the county of their choice. Responses were mapped and correlation analyses were conducted among the responses to determine factors associated with giant ragweed populations. Respondents rated giant ragweed as the most or one of the most difficult weeds to manage in 45% of 421 U.S. counties responding, and 57% of responding counties reported giant ragweed populations with herbicide resistance to acetolactate synthase inhibitors, glyphosate, or both herbicides. Results suggest that giant ragweed is increasing in crop fields outward from the east-central U.S. Corn Belt in most directions. Crop produ...
... Clarence J. Swanton, Kris J. Mahoney, Kevin Chandler, and Robert H. Gulden*. ... ragweed (Amb... more ... Clarence J. Swanton, Kris J. Mahoney, Kevin Chandler, and Robert H. Gulden*. ... ragweed (Ambrosia artemisiifolia L.), and velvetleaf (Abutilon theophrasti Medic.) in corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and dry bean (Phaseolus vulgaris L.) may be 2 to ...
Mahoney, K. J. and Gillard, C. L. 2014. Plant health and yield of dry bean not affected by strobi... more Mahoney, K. J. and Gillard, C. L. 2014. Plant health and yield of dry bean not affected by strobilurin fungicides under disease-free or simulated hail conditions. Can. J. Plant Sci. 94: 1385–1389. Strobilurin fungicides have been advocated to manage plant stress, optimize plant health, and increase yields of several crops. Studies were conducted in 2006, 2007, 2008, and 2009 to determine if azoxystrobin or pyraclostrobin induced plant health effects and increased yield of dry bean grown under conditions with very low levels of foliar disease and with the application of a simulated hail stress treatment. Azoxystrobin (125 g a.i. ha−1) and pyraclostrobin (100 g a.i. ha−1) applied at the start of flowering reduced the percentage of harvested dry bean seeds that were discoloured or misshaped (i.e., pick value) to 2.06 and 2.15%, respectively compared with 2.4% for the untreated control. Increased seed quality of edible legumes has been identified as a plant health benefit induced by str...
Mahoney, K. J., Nurse, R. E. and Sikkema, P. H. 2014. The effect of hard water, spray solution st... more Mahoney, K. J., Nurse, R. E. and Sikkema, P. H. 2014. The effect of hard water, spray solution storage time, and ammonium sulfate on glyphosate efficacy and yield of glyphosate-resistant corn. Can. J. Plant Sci. 94: 1401–1405. Effects of ammonium sulfate (AMS) on reduced glyphosate rates are well documented; however, these rates are not used by farmers. Studies in 2011 and 2012 determined the effects of AMS and hard water on glyphosate applied at a field rate. AMS (0 or 2.5 L ha−1) and glyphosate (900 g a.e. ha−1) were added to distilled or hard water carriers. Glyphosate plus AMS, in either distilled or hard water, did not usually affect velvetleaf, pigweed species, common ragweed, common lambsquarters and large crabgrass above-ground biomass and density 8 wk after treatment (WAT); however, velvetleaf biomass was reduced with the addition of AMS to glyphosate. Compared with the weedy control 8 WAT, glyphosate plus AMS reduced velvetleaf biomass by 93%, while treatments with no AMS ...
Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitativ... more Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitative data regarding its pattern and mechanisms of spread in crop fields are lacking. To address this gap, we conducted a Web-based survey of certified crop advisors in the U.S. Corn Belt and Ontario, Canada. Participants were asked questions regarding giant ragweed and crop production practices for the county of their choice. Responses were mapped and correlation analyses were conducted among the responses to determine factors associated with giant ragweed populations. Respondents rated giant ragweed as the most or one of the most difficult weeds to manage in 45% of 421 U.S. counties responding, and 57% of responding counties reported giant ragweed populations with herbicide resistance to acetolactate synthase inhibitors, glyphosate, or both herbicides. Results suggest that giant ragweed is increasing in crop fields outward from the east-central U.S. Corn Belt in most directions. Crop produ...
Five experiments were conducted over a 2-yr period (2013 and 2014) to evaluate POST herbicides in... more Five experiments were conducted over a 2-yr period (2013 and 2014) to evaluate POST herbicides in winter wheat fields with a history of glyphosate-resistant (GR) horseweed. Control 4 wk after treatment (WAT) with pyrasulfotole + bromoxynil was 95%. Control 8 WAT with 2,4-D, dicamba + MCPA + mecoprop, clopyralid, and pyrasulfotole + bromoxynil ranged from 89 to 97%; these herbicides also reduced GR horseweed density and biomass by 97 to 99%. Single mode of action herbicides like 2,4-D controlled GR horseweed; however, multiple modes of action should be used to prevent populations from becoming incrementally more resistant under repeated selection pressure.
Mahoney, K. J., Vyn, R. J. and Gillard, C. L. 2015. The effect of pyraclostrobin on soybean plant... more Mahoney, K. J., Vyn, R. J. and Gillard, C. L. 2015. The effect of pyraclostrobin on soybean plant health, yield, and profitability in Ontario. Can. J. Plant Sci. 95: 285–292. Prophylactic fungicides have been advocated to manage foliar diseases, optimize plant heath, and increase yields. Studies were conducted in 2009, 2010, and 2011 using 20 soybean cultivars to determine if pyraclostrobin, a strobilurin, induced plant health effects to increase yield and profitability under conditions with low levels of foliar disease. Pyraclostrobin applied at the R3 stage significantly reduced leaf defoliation caused by brown spot (Septoria glycines Hemmi) compared with the untreated control with 27 and 45% defoliation, respectively, across all cultivars. Pyraclostrobin delayed maturity, but the response varied among cultivars. For example, cultivars with low levels of leaf defoliation responded with an increase in the number of days to maturity, whereas cultivars with high levels of defoliation...
Field experiments in 2013 and 2014 examined corn (Zea mays L.) tolerance to acetyl-coenzyme A car... more Field experiments in 2013 and 2014 examined corn (Zea mays L.) tolerance to acetyl-coenzyme A carboxylase (ACCase) inhibiting herbicides in a scenario where they would have been used to terminate a failed corn stand prior to replanting. To simulate this, herbicides were applied 1 wk or 1 d preplant (PP) and several parameters were measured. Corn injury 1, 2, 4, or 8 wk after emergence (WAE) was similar to the untreated control, regardless of herbicide, rate, or PP application timing. Across herbicides and rates, PP timing did not affect plant stand and aboveground biomass 2 WAE, plant height 4 WAE, or yield. Across application timings, plant stand and aboveground biomass were similar to the untreated control, regardless of herbicide treatment or rate; however, some herbicides reduced height and (or) yield. For example, compared with the untreated control, fluazifop-p-butyl (75 and 150 g ha−1) and sethoxydim (300 g ha−1) each reduced height by about 3%, while clethodim (30 and 60 g h...
Abstract: Populations of glyphosate-resistant (GR) Canada fleabane and GR giant ragweed can be fo... more Abstract: Populations of glyphosate-resistant (GR) Canada fleabane and GR giant ragweed can be found in several locations in southwestern Ontario. While these species can be managed individually, a scenario has developed where both species are present in GR soybean. Ten separate field experiments (five with Canada fleabane and five with giant ragweed) were conducted over a 2-yr period (2013-2014) in soybean to evaluate preplant (PP) herbicide tank mixtures that could control both weed species if they were present in the same field. Herbicides were rated for soybean injury, weed control, population density, and aboveground biomass. Two- and three-way tank mixtures containing amitrole (i.e., glyphosate + amitrole, glyphosate + amitrole + saflufenacil, and glyphosate + amitrole + 2,4-D) were among the most effective treatments. For example, control of GR Canada fleabane and GR giant ragweed was at least 92% at 4 wk after treatment (WAT) and weed density and biomass were generally similar to the weed-free control. However, without amitrole, the best PP herbicide option was a three-way tank mixture of glyphosate + saflufenacil + 2,4-D which provided improved control and greater reductions in density and biomass compared with the two-way glyphosate tank mixtures containing saflufenacil or 2,4-D.
Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitativ... more Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitative data regarding its pattern and mechanisms of spread in crop fields are lacking. To address this gap, we conducted a Web-based survey of certified crop advisors in the U.S. Corn Belt and Ontario, Canada. Participants were asked questions regarding giant ragweed and crop production practices for the county of their choice. Responses were mapped and correlation analyses were conducted among the responses to determine factors associated with giant ragweed populations. Respondents rated giant ragweed as the most or one of the most difficult weeds to manage in 45% of 421 U.S. counties responding, and 57% of responding counties reported giant ragweed populations with herbicide resistance to acetolactate synthase inhibitors, glyphosate, or both herbicides. Results suggest that giant ragweed is increasing in crop fields outward from the east-central U.S. Corn Belt in most directions. Crop produ...
... Clarence J. Swanton, Kris J. Mahoney, Kevin Chandler, and Robert H. Gulden*. ... ragweed (Amb... more ... Clarence J. Swanton, Kris J. Mahoney, Kevin Chandler, and Robert H. Gulden*. ... ragweed (Ambrosia artemisiifolia L.), and velvetleaf (Abutilon theophrasti Medic.) in corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and dry bean (Phaseolus vulgaris L.) may be 2 to ...
Mahoney, K. J. and Gillard, C. L. 2014. Plant health and yield of dry bean not affected by strobi... more Mahoney, K. J. and Gillard, C. L. 2014. Plant health and yield of dry bean not affected by strobilurin fungicides under disease-free or simulated hail conditions. Can. J. Plant Sci. 94: 1385–1389. Strobilurin fungicides have been advocated to manage plant stress, optimize plant health, and increase yields of several crops. Studies were conducted in 2006, 2007, 2008, and 2009 to determine if azoxystrobin or pyraclostrobin induced plant health effects and increased yield of dry bean grown under conditions with very low levels of foliar disease and with the application of a simulated hail stress treatment. Azoxystrobin (125 g a.i. ha−1) and pyraclostrobin (100 g a.i. ha−1) applied at the start of flowering reduced the percentage of harvested dry bean seeds that were discoloured or misshaped (i.e., pick value) to 2.06 and 2.15%, respectively compared with 2.4% for the untreated control. Increased seed quality of edible legumes has been identified as a plant health benefit induced by str...
Mahoney, K. J., Nurse, R. E. and Sikkema, P. H. 2014. The effect of hard water, spray solution st... more Mahoney, K. J., Nurse, R. E. and Sikkema, P. H. 2014. The effect of hard water, spray solution storage time, and ammonium sulfate on glyphosate efficacy and yield of glyphosate-resistant corn. Can. J. Plant Sci. 94: 1401–1405. Effects of ammonium sulfate (AMS) on reduced glyphosate rates are well documented; however, these rates are not used by farmers. Studies in 2011 and 2012 determined the effects of AMS and hard water on glyphosate applied at a field rate. AMS (0 or 2.5 L ha−1) and glyphosate (900 g a.e. ha−1) were added to distilled or hard water carriers. Glyphosate plus AMS, in either distilled or hard water, did not usually affect velvetleaf, pigweed species, common ragweed, common lambsquarters and large crabgrass above-ground biomass and density 8 wk after treatment (WAT); however, velvetleaf biomass was reduced with the addition of AMS to glyphosate. Compared with the weedy control 8 WAT, glyphosate plus AMS reduced velvetleaf biomass by 93%, while treatments with no AMS ...
Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitativ... more Giant ragweed has been increasing as a major weed of row crops in the last 30 yr, but quantitative data regarding its pattern and mechanisms of spread in crop fields are lacking. To address this gap, we conducted a Web-based survey of certified crop advisors in the U.S. Corn Belt and Ontario, Canada. Participants were asked questions regarding giant ragweed and crop production practices for the county of their choice. Responses were mapped and correlation analyses were conducted among the responses to determine factors associated with giant ragweed populations. Respondents rated giant ragweed as the most or one of the most difficult weeds to manage in 45% of 421 U.S. counties responding, and 57% of responding counties reported giant ragweed populations with herbicide resistance to acetolactate synthase inhibitors, glyphosate, or both herbicides. Results suggest that giant ragweed is increasing in crop fields outward from the east-central U.S. Corn Belt in most directions. Crop produ...
Five experiments were conducted over a 2-yr period (2013 and 2014) to evaluate POST herbicides in... more Five experiments were conducted over a 2-yr period (2013 and 2014) to evaluate POST herbicides in winter wheat fields with a history of glyphosate-resistant (GR) horseweed. Control 4 wk after treatment (WAT) with pyrasulfotole + bromoxynil was 95%. Control 8 WAT with 2,4-D, dicamba + MCPA + mecoprop, clopyralid, and pyrasulfotole + bromoxynil ranged from 89 to 97%; these herbicides also reduced GR horseweed density and biomass by 97 to 99%. Single mode of action herbicides like 2,4-D controlled GR horseweed; however, multiple modes of action should be used to prevent populations from becoming incrementally more resistant under repeated selection pressure.
Mahoney, K. J., Vyn, R. J. and Gillard, C. L. 2015. The effect of pyraclostrobin on soybean plant... more Mahoney, K. J., Vyn, R. J. and Gillard, C. L. 2015. The effect of pyraclostrobin on soybean plant health, yield, and profitability in Ontario. Can. J. Plant Sci. 95: 285–292. Prophylactic fungicides have been advocated to manage foliar diseases, optimize plant heath, and increase yields. Studies were conducted in 2009, 2010, and 2011 using 20 soybean cultivars to determine if pyraclostrobin, a strobilurin, induced plant health effects to increase yield and profitability under conditions with low levels of foliar disease. Pyraclostrobin applied at the R3 stage significantly reduced leaf defoliation caused by brown spot (Septoria glycines Hemmi) compared with the untreated control with 27 and 45% defoliation, respectively, across all cultivars. Pyraclostrobin delayed maturity, but the response varied among cultivars. For example, cultivars with low levels of leaf defoliation responded with an increase in the number of days to maturity, whereas cultivars with high levels of defoliation...
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