5 results
Herbicide programs for control of glyphosate-resistant canola (Brassica napus) in glyphosate-resistant soybean
- Allyson Mierau, Moria E. Kurtenbach, Eric N. Johnson, Robert H. Gulden, Jessica D. Weber, William E. May, Christian J. Willenborg
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- Journal:
- Weed Technology / Volume 34 / Issue 4 / August 2020
- Published online by Cambridge University Press:
- 13 January 2020, pp. 540-546
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Glyphosate-resistant (GR) canola is a widely grown crop across western Canada and has quickly become a prolific volunteer weed. Glyphosate-resistant soybean is rapidly gaining acreage in western Canada. Thus, there is a need to evaluate herbicide options to manage volunteer GR canola in GR soybean crops. We conducted an experiment to evaluate the efficacy of various PRE and POST herbicides applied sequentially to volunteer GR canola and to evaluate soybean injury caused by these herbicides. Trials were conducted across Saskatchewan and Manitoba in 2014 and 2015. All treatments provided a range of suppression (>70%) to control (>80%) of volunteer canola. All treatments with the exception of the glyphosate-treated control reduced aboveground canola biomass by an average of 96%. As well, canola seed contamination was reduced from 36% to less than 5% when a PRE and POST herbicide were both used. Moreover, all combinations of herbicides used had excellent crop safety (<10%). All PRE and POST herbicide combinations provided better control of volunteer canola compared with the glyphosate-only control, but tribenuron followed by bentazon and tribenuron followed by imazamox plus bentazon provided solutions that were low cost, currently available (registered in western Canada), and had the potential to minimize development of herbicide resistance in other weeds.
Pollen flow between herbicide-resistant Brassica napus is the cause of multiple-resistant B. napus volunteers
- Linda Hall, Keith Topinka, John Huffman, Lesley Davis, Allen Good
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- Journal:
- Weed Science / Volume 48 / Issue 6 / December 2000
- Published online by Cambridge University Press:
- 20 January 2017, pp. 688-694
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A field in which Brassica napus volunteers were not controlled by several applications of glyphosate was investigated in 1998. This field had been planted with glufosinate-resistant and imidazolinone-resistant B. napus in 1997 and was adjacent to a field that had grown glyphosate-resistant B. napus. Mature volunteer B. napus were collected on a 50- by 100-m grid in the field. Progeny from 34 volunteers were sprayed with glyphosate at 440 g ae ha−1, and the survivors were sprayed with either glufosinate or imazethapyr at 400 or 50 g ai ha−1, respectively. Where seed numbers permitted (14 volunteers), seedlings were also sprayed sequentially with glyphosate, glufosinate, and imazethapyr, at 440 g ae ha−1, 400 g ai ha−1, and 50 g ai ha−1, respectively. In total, 15 volunteers had progeny that were between 66 and 82% resistant to glyphosate, consistent with the predicted 3:1 resistant : susceptible ratio. Volunteer B. napus plants with glyphosate-resistant seedlings were most common close to the putative pollen source; however, a plant with glyphosate-resistant progeny was collected 500 m from the adjacent field edge. Seedlings from all nine volunteers collected from the glufosinate-resistant area showed multiple resistance to glyphosate and glufosinate, whereas seedlings from 10 of 20 volunteers collected from the imidazolinone-resistant area showed resistance to imazethapyr and glyphosate. DNA extraction and restriction fragment length polymorphism (RFLP) analysis of seedlings confirmed that mature B. napus volunteers were hybrids resulting from pollen transfer rather than inadvertent seed movement between fields. Two seedlings from the 924 screened were resistant to all three herbicides. Progeny from these self-pollinated individuals were resistant to glyphosate and glufosinate at the predicted 3:1 resistant : susceptible ratio and resistant to imazethapyr at the predicted 15:1 resistant : susceptible ratio. Sequential crossing of three herbicide-resistant varieties is the most likely explanation for the observed multiple herbicide resistance. Integrated management techniques, including suitable crop and herbicide rotations, herbicide mixtures, and nonchemical controls should be used to reduce the incidence and negative effect of B. napus volunteers with multiple herbicide resistance.
Effect of Harvest Timing on Dormancy Induction in Canola Seeds
- Teketel A. Haile, Steven J. Shirtliffe
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- Journal:
- Weed Science / Volume 62 / Issue 3 / September 2014
- Published online by Cambridge University Press:
- 20 January 2017, pp. 548-554
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Seedbank persistence in canola seeds is related to their potential to develop secondary dormancy. This can result in volunteer weed problems many years after canola production. The potential to be induced into secondary dormancy is controlled by both the canola genetics and the environment of the mother plant. However, the effect of time of harvesting on secondary dormancy potential is not known. The objective of this study was to determine the effect of harvest timing on potential to develop seed dormancy in canola. Six harvest samples were collected weekly from two canola genotypes (5440 and 5020) starting from 10 to 20% seed color change on the main stem until they were fully ripened. Freshly harvested seeds of 5440 and 5020 showed 13 and 16% primary dormancy at 32 and 33 d after flowering (DAF), respectively, but dormancy decreased with harvest timings and no dormancy was observed when seeds were fully mature (78 DAF). After dormancy induction, 10% of 5440 seeds were dormant at 32 DAF, but 94% of seeds were dormant at 78 DAF. Similarly, 70% of 5020 seeds were dormant at 33 DAF, but 90% of seeds were dormant at 68 DAF. Thus, seeds had lower potential to secondary dormancy at early development but have a high potential to secondary dormancy induction at full maturity. This study suggests that windrowing these canola genotypes at the recommended time (60% seed color change on the main stem) may reduce ability of the seed to develop secondary dormancy and thus reduce the persistence of seeds in the soil seedbank.
Fitness of double vs. single herbicide–resistant canola
- Marie-Josée Simard, Anne Légère, Ginette Séguin-Swartz, Harikumar Nair, Suzanne Warwick
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- Journal:
- Weed Science / Volume 53 / Issue 4 / August 2005
- Published online by Cambridge University Press:
- 20 January 2017, pp. 489-498
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Since 1995, canola cultivars with herbicide resistance (HR) have been readily adopted by Canadian producers. Gene flow between these cultivars with different HR traits has led to the occurrence of double herbicide–resistant (2HR) volunteers. To evaluate the fitness of canola volunteers with double HR, we compared three 2HR combinations to each of their parent single-HR plants (1HR: glufosinate-R, imidazolinone-R, glyphosate-R) commercial canola lines in separate greenhouse experiments. The replacement series design included five ratios of 2HR vs. 1HR plants at a single density of 129 plants m−2 and three stress treatments: herbicide application with either glufosinate, imazethapyr, or glyphosate; competition with a wheat crop; and a control without herbicide or wheat competition. Fitness indicators included aboveground biomass at 5 and 12 to 16 wk, seed production, and reproductive allocation. The 2HR plants showed delayed reproductive growth but were generally as competitive as 1HR commercial lines. Plant biomass of 2HR canola was comparable to or greater than 1HR canola, whereas seed biomass of 2HR canola was less than that of 1HR canola in half of the cases, likely because of delayed reproductive growth and early harvesting. Glufosinate–glyphosate 2HR was the fittest combination. Herbicide application had little effect on 2HR biomass at harvest, except for imazethapyr, which reduced the biomass and seed production of 2HR plants with imidazolinone-glyphosate resistance by 30%. The latter effect could have been from the unsuspected presence of 2HR plants with only one of the two acetolactate synthase mutations conferring resistance to imidazolinones. Wheat competition reduced fitness values of both 2HR and 1HR canola similarly, but seed production was still 64% that of the controls. Overall, there was little indication of reduced fitness in 2HR canola compared with commercial 1HR varieties.
Emergence timing of volunteer canola in spring wheat fields in Manitoba
- Arvel N. Lawson, Rene C. Van Acker, Lyle F. Friesen
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- Journal:
- Weed Science / Volume 54 / Issue 5 / October 2006
- Published online by Cambridge University Press:
- 20 January 2017, pp. 873-882
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Observational studies of weed emergence provide essential data for the creation and testing of predictive emergence models, with data ideally being collected from a wide range of sites representing a range of environments under which the seedlings of a given species emerge. The spring emergence of genetically engineered glyphosate-resistant volunteer canola was monitored in 20 farmers' commercial wheat fields over 2 yr, 2003 and 2004, in the southwestern region of Manitoba, Canada. Three different tillage systems, low-disturbance direct-seeded, high-disturbance direct-seeded, and conventionally tilled fields, were represented in this sample. Tillage system did not significantly influence the emergence periodicity of volunteer canola, but did influence total densities observed. Total volunteer canola densities in the surveyed fields were variable and ranged from 6 to 2,015 seedlings m−2. Conventionally tilled fields had the lowest densities of volunteer canola seedlings, and high-disturbance direct-seeded fields (no autumn tillage) had the highest densities. Volunteer canola is a relatively early spring emerging plant species requiring minimal accumulated growing degree days for emergence (calculated using a base temperature of 5 C). Emergence curves were steep, with a short window of volunteer canola emergence either prior to or within a spring-seeded wheat crop. To determine what proportion of autumn-broadcast canola seed (simulated harvest losses) would recruit the following spring and the influence of fall or spring tillage on this recruitment, a small plot experiment also was conducted at three sites. The following spring the percentage of canola seedlings that emerged ranged from 1.3 to 9.4% of the seed broadcast, depending upon the tillage treatment. The effect of tillage treatment on canola densities in the small plot experiment was similar to the field survey results.