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Green pigweed [Amaranthus powellii S. Wats.] is a competitive, annual, broadleaf weed that can significantly reduce soybean yield due to rapid early growth and biomass production. As a consequence of green pigweed's high competitiveness with crops, the weed species is generally managed with the use of herbicides; this may, however, lead to the selection of resistance. A green pigweed biotype with resistance to MCPA, mecoprop, dichlorprop-p, aminocyclopyrachlor (synthetic auxins), and imazethapyr (acetolactate synthase-(ALS)-inhibitor) was recently confirmed in Ontario, Canada. Research was conducted to identify alternative effective preemergence (PRE) and postemergence (POST) herbicides for the control of multiple-herbicide-resistant (MHR) green pigweed in Ontario soybean production. Four field trials, two with PRE and two with POST herbicides were conducted near Dresden, Ontario in 2019 and 2020. Visible soybean injury, green pigweed control, density, aboveground biomass, and soybean yield were evaluated following application with 19 PRE herbicide treatments and 12 POST herbicide treatments in separate studies. At 8 wk after application (WAA), pyroxasulfone/flumioxazin applied PRE controlled green pigweed 95% and was the most effective soil-applied herbicide. In the POST study, glyphosate was the most effective herbicide, controlling green pigweed 94% at 8 WAA. Imazethapyr, applied PRE or POST did not control this green pigweed biotype as it is also resistant to ALS-inhibitors. Control with other ALS-inhibiting herbicides as well as with PPO-inhibiting herbicides was variable, and further research is needed to determine the reason for variable control with these herbicides. [ABSTRACT FROM AUTHOR]

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.)

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.)

Currently, there are no published data available to describe the influence of herbicide residues on establishment and function of fall-seeded cover crops. Field experiments were conducted in 2012/2013 and 2013/2014 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and function of oat ( Avena sativa L.), hairy vetch ( Vicia villosa L.), oilseed radish ( Raphanus sativus L.) and cereal rye ( Secale cereale L.). These cover crops were planted three months after application of imazethapyr at 100 and 200 g ha −1 , s-metolachlor/atrazine plus mesotrione at 2880 + 140 and 5760 + 280 g ha −1 , and saflufenacil/dimethenamid-p at 735 and 1470 g ha −1 . Imazethapyr residues caused up to 65 and 30% visible injury to oilseed radish at 1 and 4 WAE, respectively. Plant light attenuation, shoot dry weight and shoot nitrate-nitrogen uptake from imazethapyr residues three months after application were reduced up to 77, 34 and 43%, respectively in oilseed radish compared to non-treated control. Oat, hairy vetch and cereal rye were not negatively impacted by any of the herbicide residues tested. Preliminary evidence suggests that oat, hairy vetch and cereal rye may be safely seeded three months after saflufenacil/dimethenamid-p, s-metolachlor/atrazine plus mesotrione, and imazethapyr applied PRE at the currently registered rates. It is recommended however, that oilseed radish not be seeded three months after imazethapyr application. [ABSTRACT FROM AUTHOR]

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 discusses a survey that documented the distribution of glyphosate-resistant (GR) giant ragweed in southwestern Ontario. It cites the collection of giant ragweed seed from 102 sites in four counties during the autumn of 2009 and 2010 prior to soybean harvest. GR giant ragweed was confirmed at 47 new locations in Essex, Chatham-Kent and Lambton counties. The results indicate that GR giant ragweed biotypes occur across a greater area in southwestern Ontario than originally thought.

The article discusses field studies conducted in 2009 and 2010 at three Ontario locations to determine the biologically effective rate of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. Temperatures and precipitation influenced the rate of saflufenacil/dimethenamid-p needed for the control of annual weeds. The potential of saflufenacil/dimethenamid-p as a set-up treatment prior to a postemergence (POST) glyphosate application is also explored.

The article discusses results of a study that examines the ammonium sulfate (AMS) and water hardness effect on glyphosate and glufosinate activity in corn in fields near Harrow and Ridgetown, Ontario. The study showed that water hardness has no effect on control of velvetleaf, common lambsquarters, redroot pigweed and annual grasses green foxtail and barnyardgrass. It concludes that AMS and water hardness have little benefit on glyphosate efficacy in corn.

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]

Xanthomonas gardneri is the common causal agent of bacterial spot affecting field tomatoes in Ontario, Canada but spread during seedling transportation and transplanting is poorly understood. Spread during transportation and irrigation was determined by placing symptomatic seedlings at the top of a simulated plug trailer with healthy seedlings 30.5, 61.0, 91.5, and 122 cm below to assess pathogen movement with different irrigation treatments. The incidence of seedlings with symptoms 14 days after irrigation in the top to bottom (3.9%) and bottom to top (5.4%) treatments was greater than the dip treatment (0.4%). Symptoms were found at all distances below the inoculation point. A second set of experiments looked at spread in a transplanter by placing wet or dry symptomatic seedlings through the transplanter prior to healthy seedlings. Epiphytic X. gardneri was found on healthy seedlings from all diseased treatments 14 days after treatment, indicating transmission of X. gardneri during transplanting. A third set of experiments assessed the impact of transplanter transmission in the field by monitoring symptom appearance in initially healthy seedlings planted in rows with either machine-transplanted diseased plants or hand-planted diseased plants. There was no difference in the time to symptom appearance, except for one plant position which was not in the direction of transplanting. Thus, factors other than contaminated transplanters may be more important in X. gardneri transmission under field conditions. Best management practices for bacterial spot in field tomatoes should consider irrigation practices in plug trailers, while the contribution of contaminated transplanters to epidemics is likely limited. • Bacterial spot symptom appearance was reduced by dip irrigating transplant trays compared to overhead irrigation. • Xanthomonas gardneri was recovered from foliage after contact with transplanter surfaces exposed to symptomatic plants. • Bacterial spot symptom appearance in field trials was not associated with the use of contaminated transplanting equipment. [ABSTRACT FROM AUTHOR]

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]

There is little information published on the effect of residues from postemergence (POST) applications of foramsulfuron and preemergence (PRE) applications of isoxaflutole, and isoxaflutole plus atrazine in the year after application on vegetable crops. Three trials were established from 2000 to 2002 in Ontario to determine the effects of residues of foramsulfuron, isoxaflutole, and isoxaflutole plus atrazine on cabbage, processing pea, potato, sugar beet, and tomato 1 year after application. Aside from a reduction in sugar beet plant stand, there were no visual injury symptoms in any crop at 7, 14, and 28 days after emergence (DAE) in any of the herbicide carryover treatments. Isoxaflutole residues reduced shoot dry weight and yield as much as 27% and 28% in cabbage, and 57% and 60% in sugar beets, respectively. The addition of atrazine to isoxaflutole caused further reductions in shoot dry weight and yield of cabbage and sugar beet. Isoxaflutole plus atrazine residues reduced shoot dry weight and yield as much as 42% and 43% in cabbage, and 58% and 82% in sugar beets, respectively. There were no adverse effects on shoot dry weight and yield of processing pea, potato, and tomato from isoxaflutole or isoxaflutole plus atrazine residues in the year following application. Foramsulfuron residues at either rate did not reduce shoot dry weight or yield of any crops 1 year after application. Based on these results, it is recommended that cabbage and sugar beet not be grown in the year following the PRE application of isoxaflutole or isoxaflutole plus atrazine. [ABSTRACT FROM AUTHOR]