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Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Glyphosate + dicamba has provided variable glyphosate-resistant Canada fleabane (GRCF) control in glyphosate/dicamba-resistant (GDR) soybean. Previous research has indicated improved GRCF control when a third herbicide was added to glyphosate + dicamba, though research is limited. The objective of this research was to ascertain if the level and consistency of GRCF control can be improved when adding tiafenacil, metribuzin, bromoxynil, pyraflufen-ethyl/2,4-D, 2,4-D ester, halauxifen-methyl or saflufenacil to glyphosate + dicamba applied preplant (PP) in GDR soybean. Four field trials were conducted in 2020 and 2021 in commercial fields in southwestern Ontario, Canada. Glyphosate + dicamba controlled GRCF 57, 93 and 94% at 2, 4 and 8 WAA, respectively. Adding bromoxynil to glyphosate + dicamba improved GRCF control from 57 to 77% at 2 WAA; adding saflufenacil to glyphosate + dicamba improved GRCF control from 57 to 92, 93 to 99, and 94 to 99% at 2, 4 and 8 WAA, respectively. All three-way tank-mixtures improved the consistency of GRCF control, except for glyphosate + dicamba + 2,4-D ester at 2 WAA, glyphosate + dicamba + 2,4-D ester, tiafenacil or metribuzin at 4 WAA, and glyphosate + dicamba + tiafenacil or bromoxynil at 8 WAA. This study concludes that the level and consistency of GRCF control was improved when saflufenacil was added to a PP application of glyphosate + dicamba in soybean. [ABSTRACT FROM AUTHOR]

The article presents a study which sought to examine the efficacy of several preplant (PP) herbicides in controlling glyphosate-resistant (GR) giant ragweed or Ambrosia trifida L. prior to soybean planting in southwestern Ontario. The researchers conducted field trials using PP burndown and PP burndown plus residual herbicides in farms with GR giant ragweed. It was found out that residual control with glyphosate plus linuron led to soybean yield equivalent to the weed-free check.

Abstract: Pyroxasulfone is a new herbicide being considered for registration in sweet maize in Canada; however, there is still little information on the doses required to provide 90% control of annual grass and broadleaved weeds found in southwestern Ontario. The objective of this study was to determine pyroxasulfone doses that would provide at least 90% control of several economically important weeds, without impacting final sweet maize yield by more than 5% in comparison to a weed-free control. Six field trials were conducted over a two-year period (2007 and 2008) at three Ontario locations to evaluate the effectiveness of pyroxasulfone at doses ranging from 31.25 to 1000 g a.i. ha−1. The doses required to reduce weed biomass by at least 90% (I90) varied by weed species. Doses of 93, 499, and 111 g a.i. ha−1 were required to reduce the biomass by 90% of redroot pigweed, common lambsquarters and green foxtail, respectively. There was greater than 95% control of velvetleaf, large crabgrass and barnyardgrass with 31.25 g a.i. ha−1, the lowest dose tested. Sweet maize yield could not be consistently maintained within 5% of the weed-free control. There are several factors that may have contributed to the reduced yield, including soil texture effects, competition as a result of poor common lambsquarters control, and hybrid sensitivity. These results show that biologically effective weed control with pyroxasulfone may be achieved at lower than proposed doses for several weed species; it remains unclear if this is economically sustainable due to the potential impacts on yield. [Copyright &y& Elsevier]

Abstract: Four field trials were conducted over a two-year period at Exeter (2005, 2006), Harrow (2006) and Ridgetown (2006), Ontario to evaluate the tolerance of pinto and Small Red Mexican (SRM) beans to the pre-emergence application of dimethenamid-p at 693 and 1386gaiha−1, s-metolachlor at 1600 and 3200gaiha−1, pyroxasulfone at 209 and 418gaiha−1, imazethapyr at 75 and 150gaiha−1, linuron at 1125 and 2250gaiha−1, flumetsulam at 70 and 140gaiha−1 and cloransulam-methyl at 35 and 70gaiha−1. All treatments including the non-treated control were maintained weed free during the growing season. Dimethenamid-p and s-metolachlor, especially at high doses, caused up to 19% visual injury to pinto and SRM, but these injuries were transient and had no effect on maturity and yield. Pyroxasulfone and linuron caused as much as 33% visual injury and reduced plant height, shoot dry weight and yield by up to 29, 36 and 25%, respectively. Imazethapyr, flumetsulam and cloransulam-methyl caused less than 5% visual injury and had no adverse effect on plant height, shoot dry weight, seed moisture content and yields of pinto and SRM beans. Based on these results dimethenamid-p, s-metolachlor, imazethapyr, flumetsulam and cloransulam-methyl applied pre-emergence have potential for inclusion in a weed management program for pinto and SRM beans. However, pyroxasulfone and linuron, applied pre-emergence at the doses evaluated do not have an adequate margin of crop safety for use in pinto and SRM bean production. [Copyright &y& Elsevier]

Abstract: There are few pre-transplant herbicides for weed control in cole crops in Ontario. Three field trials were established each year in 2003, 2004, and 2005 at Ridgetown, Ontario, Canada to evaluate broccoli, cabbage, and cauliflower tolerance to oxyfluorfen (560 and 1120g a.i./ha), dimethenamid-p (750 and 1500g a.i./ha), sulfentrazone (100 and 200g a.i./ha), and a tank-mix of dimethenamid-p plus sulfentrazone (750+100 and 1500+200g a.i./ha), representing once and twice the proposed use dose for each herbicide/tankmix. Treatments included a non-treated weed-free control. Oxyfluorfen, dimethenamid-p, sulfentrazone, and dimethenamid-p plus sulfentrazone applied pre-transplant at the proposed and twice the proposed use dose in broccoli, cabbage, and cauliflower did not cause any visual injury, and did not reduce number of heads produced, head weight or yield in all nine trials conducted. Based on these results, oxyfluorfen, dimethenamid-p, sulfentrazone, and dimethenamid-p plus sulfentrazone all have an acceptable level of crop safety for use at the proposed dose in broccoli, cabbage, and cauliflower. [Copyright &y& Elsevier]

Ontario otebo bean growers have few herbicide options available for weed management. Six field trials were conducted in Ontario, Canada, over a 2 year period (2003 and 2004) to evaluate the tolerance of otebo bean to the postemergence (POST) application of bentazon at 1080 and 2160 g ai ha−1, fomesafen at 240 and 480 g ai ha−1, sethoxydim at 500 and 1000 g ai ha−1, quizalofop-p-ethyl at 72 and 144 g ai ha−1, imazamox plus fomesafen at 25 + 200 and 50 + 400 g ai ha−1, and imazamox plus bentazon at 25 + 600 and 50 + 1200 g ai ha−1. All treatments, including the untreated control, were maintained weed-free during the growing season. The POST application of bentazon, imazamox plus fomesafen, and imazamox plus bentazon caused as much as 9% visual injury and reduced the plant height ≤ 12%, reduced the shoot dry weight ≤ 32%, and delayed maturity but had no adverse effect on the yield of otebo bean. Fomesafen, sethoxydim, and quizalofop-p-ethyl applied POST caused as much as 8% visual injury but this was transient and had no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of otebo bean, except for quizalofop-p-ethyl, which reduced the shoot dry weight as much as 18%. Based on these results, bentazon, fomesafen, sethoxydim, quizalofop-p-ethyl, imazamox plus fomesafen, and imazamox plus bentazon applied POST have an adequate margin of crop safety for weed management in otebo bean production in Ontario. However, care must be taken to avoid spray overlaps to prevent injury from bentazon, imazamox plus fomesafen, and imazamox plus bentazon. [ABSTRACT FROM AUTHOR]

Abstract: There are few herbicide options available for weed management in adzuki beans in Ontario. Six field trials were conducted in Ontario over a 2-year period (2003 and 2004) to evaluate the tolerance of adzuki bean to the post-emergence application of bentazon, fomesafen, sethoxydim, quizalofop-p-ethyl, imazamox plus fomesafen and imazamox plus bentazon. All treatments including the non-treated control were maintained weed free for the complete growing season. The application of bentazon and imazamox plus bentazon caused visual injury and reduced plant height up to 43%, reduced shoot dry weight up to 65%, delayed maturity and reduced adzuki bean yield as much as 56%. Fomesafen, sethoxydim, quizalofop-p-ethyl, and imazamox plus fomesafen caused visual injury but this was transient and there was no adverse affect on plant height, shoot dry weight, seed moisture content and yield of adzuki bean. Fomesafen and imazamox plus fomesafen reduced shoot dry weight by 16% and delayed maturity at the high dose. Based on these results, the application of fomesafen, sethoxydim, quizalofop-p-ethyl and imazamox plus fomesafen has an adequate margin of crop safety for weed management in adzuki beans in Ontario, but bentazon and imazamox plus bentazon do not. [Copyright &y& Elsevier]

Pepper growers currently have limited access to many effective broadleaf herbicides. Field trials were conducted over a 3-year period in Ontario to study the effect of tank mixtures of sulfentrazone (100 or 200 g⋅ha-1 a.i.) with either s-metolachlor (1200 or 2400 g⋅ha-1 a.i.) or dimethenamid-p (750 or 1500 g⋅ha-1 a.i.) on transplanted bell pepper. Under weed-free conditions, there was no visual injury or reduction in plant height, fruit number, fruit size, or marketable yield of transplanted pepper with pretransplant applications Of sulfentrazone applied in tank mixtures with s-metolachlor or dimethenamid-p. The tank mixture of sulfentrazone + s-metolachlor gave greater than 85% control of redroot pigweed (Amaranthus retroflexus) and eastern black nightshade (Solanum ptycanthum), but only 70% to 76% control of velvetleaf (Abutilon theophrasti), common ragweed (Ambrosia artemisiifolia), and common lambsquarters (Chenopodium album). The combination of sulfentrazone + dimethenamid-p provided good to excellent control of all weed species except velvetleaf. Based on this study, sulfentrazone and dimethenamid-p have potential for minor use registration in pepper. [ABSTRACT FROM AUTHOR]

Combining herbicides and fungicides can improve production efficiency; however, there is little information on the effect of these mixtures on weed control and processing tomato crop response. Six field trials were conducted from 2002 to 2004 in Ontario to study the effect of rimsulfuron and thifensulfuron applied alone or in combination with metribuzin and with or without chlorothalonil or copper fungicides on processing tomato. There was no visual injury or reduction in marketable yield of processing tomato with rimsulfuron or thifensulfuron alone or when tank-mixed with chlorothalonil or copper hydroxide. Rimsulfuron, thifensulfuron, rimsulfuron plus metribuzin, and thifensulfuron plus metribuzin could he tank-mixed with chlorothalonil without a reduction in weed control. However, efficacy of rimsulfuron and thifensulfuron were reduced when tank-mixed with copper hydroxide. The reduction in weed control incited by adding copper hydroxide was overcome with a low rate 1150 g⋅ha-1 a.i.) of metribuzin for thifensulfuron but not rimsulfuron. Application of rimsulfuron and thifensulfuron alone or with low rates of metribuzin and chlorothalonil could provide tomato growers with a single-pass treatment for the control of troublesome weeds and diseases. [ABSTRACT FROM AUTHOR]

Limited information exists on sweet corn (Zea mays) tolerance to postemergence (POST) applications of thifensulfuron-methyl under Ontario growing conditions. Eight sweet corn hybrids were evaluated for tolerance to thifensulfuron-methyl in four field experiments conducted in 2003 and 2004. Thifensulfuron-methyl was applied POST at 6 and 12 g·ha-1 a.i., the registered and twice the registered rate for use in soybean in Ontario. Sweet corn hybrid responses to thifensulfuron-methyl varied. Delmonte 2038 was the most sensitive to thifensuifuron-methyl and had as much as 92% visual injury, 76% height reduction, and 98% yield reduction compared to the nontreated control. Empire, GH1861, GH2298, and GH2684 hybrids showed visual injury of 53%, 55%, 53%, and 61%, height reduction of 34%, 31%, 32%, and 26% and yield reduction of 77%, 68%, 68%, and 51%, respectively. GG214, GH2547, and GSS9299 sweet corn hybrids were not as sensitive to thifensulfuron-methyl. The initial sensitivity observed in these hybrids was minimal and transient with no effect on yield. Although thifensulfuron-methyl is safe for use on some sweet corn hybrids, it has the potential to cause severe crop injury and yield reduction in other hybrids and therefore it should not be recommended for weed management in sweet corn production in Ontario. [ABSTRACT FROM AUTHOR]

Abstract: Atrazine is the most widely used herbicide in North American corn production; however, additional restrictions on its use in the near future are conceivable. Currently, a majority of commercial sweet corn fields suffer losses due to weeds, despite widespread use of atrazine. Field experiments were conducted in the primary North American production areas of sweet corn grown for processing to determine the implications of further reductions in atrazine use on weed control and crop yield. A range of atrazine doses (0–1120gha−1) applied postemergence with tembotrione (31gha−1) were tested in two hybrids differing in canopy architecture and competitive ability with weeds. Atrazine applied postemergence reduced risk (i.e. more variable outcomes) of poor herbicide performance. Atrazine doses up to 1120gha−1 with tembotrione improved grass control and broadleaf weed control in five of eight and seven of eight environments, respectively. Of the three environments which had particularly low broadleaf weed control (<50%) with tembotrione alone, sweet corn yield was improved with atrazine. Hybrid ‘Code128’ produced a taller, denser canopy which was more efficient at capturing light and competing with weeds than ‘Quickie’. As a result, greater crop competitiveness decreased risk of incomplete weed control as atrazine dose was reduced. Atrazine''s contribution to weed control and yield protection was greatest when other aspects of weed management resulted in poor weed control. Should atrazine use be further restricted or banned altogether, this research demonstrates the importance of improving other aspects of weed management systems such as herbicidal and non-chemical tactics. [Copyright &y& Elsevier]

Topramezone is a newly introduced herbicide for use in field corn (Zea mays L.) that may have potential for weed management in sweet corn. Tolerance of eight sweet corn hybrids to topramezone applied postemergence (POST) at 0, 50, 75, 100, 150, and 300 g a.i. ha-1 were studied at one Ontario location in 2000 and two locations in 2001 and 2002. Topramezone applied POST at 50, 75, 100, and 150 g·ha-1 did not cause any visual injury in Calico Belle, CNS 710, Delmonte 2038, FTF 222, FTF 246, GH 2684, Reveille, and Rival sweet corn hybrids at 7 days after treatment (DAT) and caused minimal injury (less than 5%) at 300 g·ha-1 in all hybrids. The initial sensitivity observed in these hybrids was minimal and transient with no effect on visual injury at 14 and 28 DAT. Topramezone applied POST did not reduce plant height, cob size, or marketable yield of the sweet corn hybrids included in this study. Based on these results, topramezone applied POST at the rates evaluated can be safely applied to Calico Belle, CNS 710, Delmonte 2038, FTF 222, FTF 246, GH 2684, Reveille, and Rival sweet corn. [ABSTRACT FROM AUTHOR]