Efficacy of POST glyphosate applications in combination with other POST herbicides in glyphosate-resistant corn (Zea mays L.) (original) (raw)
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Crop Protection, 2006
In glyphosate-tolerant maize, a delay in glyphosate application may be required to ensure late germinating weeds do not reach reproductive maturity. Alternatively, full season weed control may be achieved by frequent applications of glyphosate throughout the growing season. Another approach that may improve weed control and aid in the stewardship of glyphosate use is to apply a preemergence residual herbicide prior to one in-crop application of glyphosate. There is limited information on the optimal glyphosate application timing in glyphosate-tolerant maize (Zea mays) following the application of a residual herbicide. Six factorial field trials were conducted over a 2 year period (1999 and 2000) at two Ontario locations, Ridgetown, and Woodstock to evaluate the efficacy of the residual herbicide flufenacet plus metribuzin applied preplant, pre-emergence or at the maize spike stage followed by a post-emergence application of glyphosate in glyphosate-tolerant maize. At Ridgetown, crop tolerance was acceptable at all flufenacet plus metribuzin, glyphosate and flufenacet plus metribuzin followed by glyphosate application timings. Visual crop injury of up to 40% was recorded at Woodstock after the application of flufenacet plus metribuzin. Control of Amaranthus retroflexus, Ambrosia artemisiifolia, and Chenopodium album with flufenacet plus metribuzin followed by an in-crop application of glyphosate was better than with one in-crop application of glyphosate. The application timing of glyphosate and flufenacet plus metribuzin was not a significant factor in weed control or grain yield. In maize, the application of a residual herbicide such as flufenacet plus metribuzin prior to glyphosate may provide better early season weed control and allow for the delayed in-crop application of glyphosate. r
Biologically effective dose of glyphosate as influenced by weed size in corn
Canadian Journal of Plant Science, 2016
There is limited information on the effect of weed size at the time of application on glyphosate efficacy in Ontario. Eleven field trials were conducted over a 3 yr period (2010–2012) in Ontario to determine the biologically effective dose of glyphosate applied postemergence (POST) in corn at doses of 112.5–1350 g acid equivalent (a.e.) ha−1 for the control of various grass and broadleaved weed species when the weeds were 10, 20 or 30 cm in height. The GR90 for redroot pigweed, common ragweed, common lamb’s-quarters, barnyardgrass, and green foxtail were 353, 630, 621, 763, and <112.5 g a.e. ha−1 when applied at 10 cm weed height, 235, 201, 906, 868, and 296 g a.e. ha−1 when applied at 20 cm weed height, and 792, >1350, >1350, 912, and 675 g a.e. ha−1 when applied at 30 cm weed height, respectively. Corn yields were maximized when glyphosate was applied to weeds that were up to 10 cm in height, but was reduced with later glyphosate application timings. The results of this s...
Journal of Agricultural Science
Glyphosate needs to be partnered with other herbicides that have residual biological activity on ryegrass (Lolium multiflorum Lam.) to improve the efficacy and consistency of annual ryegrass control in corn. Five field experiments were conducted from 2019 to 2021 near Exeter, Ontario to evaluate various glyphosate tank mixes applied preplant (PP) in the spring in corn for the control of annual ryegrass seeded as a cover crop in the fall of the previous year (2018 to 2020). At 1 week after application (WAA), all glyphosate tank mixes evaluated provided minimal annual ryegrass control (14-28%). At 2 WAA, the addition of dimethenamid-p/saflufenacil to glyphosate improved annual ryegrass control from 55% to 68%; there was no improvement in annual ryegrass control with the other 14 tank mixes evaluated. At 3 WAA, the addition of dimethenamid-p/saflufenacil and mesotrione + rimsulfuron to glyphosate controlled annual ryegrass 91 and 90%, respectively. At 4 WAA, the addition of dimethenami...
Kansas Agricultural Experiment Station Research Reports, 2017
A study was initiated near Garden City, KS, in 2016, comparing the weed control of several herbicide treatments applied sequentially in irrigated corn. Kochia control was 95% or more with all treatments at 1 day after late postemergence application (1 DALP) and 100% regardless of treatment at 63 days after late postemergence application (63 DALP). Palmer amaranth and green foxtail control was 98 to 100% and 83 to 93%, respectively, with all preemergence treatments at 1 DALP. A second late postemergence application was needed to achieve 100% control of Palmer amaranth and green foxtail 63 DALP. The single early postemergence treatment controlled Palmer amaranth and green foxtail 90 and 91% at 63 DALP.
Control of glyphosate-resistant common ragweed in corn with preemergence herbicides
Canadian Journal of Plant Science, 2018
Four field experiments were conducted during 2016 and 2017 to evaluate the efficacy of preemergence herbicides to control of glyphosate-resistant common ragweed in corn. Dicamba, dicamba/atrazine, mesotrione+atrazine, isoxaflutole+atrazine, saflufenacil/dimethenamid-P and S-metolachlor/mesotrione/bicyclopyrone/atrazine were the most efficacious herbicides, providing 94-100% control of GR common ragweed and reducing density and biomass 98-100%.
Influence of late emerging weeds in glyphosate-resistant corn
Agricultural Sciences, 2013
Fifteen field trials were conducted from 2009 to 2011 in Ontario, Canada and Michigan, USA to determine how long glyphosate-resistant corn needs to be kept weed-free after emergence to prevent yield loss. Data were separated into two environments based on when yield loss first occurred after glyphosate application. In Environment 1 (4/15 sites) yield was not reduced when corn was kept weed-free until the 4-leaf stage. However, in Environment 2 (11/15 sites) there was no yield loss when corn was kept weed-free up to the 2-leaf stage. The most prominent weeds were velvetleaf, redroot pigweed, common ragweed, common lambsquarters and foxtail species. While later emerging weeds did not necessarily impact corn yield, weeds emerging after the 2-and 4-leaf corn stage likely produced seed that was added to the soil seed bank. Weeds emerging after 6-, 8-, and 10-leaf corn growth stages were small (low biomass/seedlings) and most likely did not reach reproductive maturity. Based on this research, corn must be maintained weed-free up to the 4-leaf stage. Any weeds emerging after that did not influence corn yield.
Efficacy of Sequential Herbicide Applications in Glufosinate- and Glyphosate-Resistant Corn
Kansas Agricultural Experiment Station Research Reports, 2019
To determine their efficacy in corn, this study compared two preemergence programs and sequential glufosinate (Interline) or glyphosate (Roundup PowerMax). Control of common sunflower and Russian thistle was excellent regardless of herbicide treatment. Preemergence herbicides alone provided no more than 78% johnsongrass control early in the season. By late season, only those plots receiving Roundup PowerMax had more than 85% johnsongrass control. However, corn yields did not differ among treatments, and all herbicides increased yield 70-97% relative to nontreated corn.
Efficacy of Preplant and Early Postemergence Herbicides in Corn
Kansas Agricultural Experiment Station Research Reports, 2017
A study was initiated near Garden City, KS, in 2016, comparing the weed control of several herbicide treatments applied sequentially for weed control in irrigated corn. Acuron (metolachlor + atrazine + mesotrione + bicyclopyrone), Clarity (dicamba), Corvus (isoxaflutole + thiencarbazone), Halex GT (metolachlor + glyphosate + mesotrione), and Lumax EZ (metolachlor + atrazine + mesotrione) were compared when combined at various ratios and timings. All combinations gave similar levels of weed control, allowing a producer to compare these tank mixes head-to-head based on prices alone.
Weed Technology, 2004
Corn and soybean were planted in narrow and wide row spacings to determine the effect of glyphosate application timing and row spacing on crop yield. Glyphosate was applied when average weed canopy height reached 5, 10, 15, 23, and 30 cm. Weeds present in these studies included velvetleaf, redroot pigweed, common ragweed, common lambsquarters, jimsonweed, barnyardgrass, fall panicum, giant foxtail, yellow foxtail, green foxtail, and eastern black nightshade. Under highly competitive growing conditions (below normal rainfall and high weed density), corn yield was first reduced when weeds reached 10 and 15 cm in height with corn planted in 38-and 76-cm rows, respectively. Under similar conditions, soybean yield was first reduced when weeds reached 15 and 23 cm with soybean planted in 19-and 38-cm rows, respectively. Yield losses occurred only in the untreated control when soybean was planted in 76-cm rows. When growing conditions were less competitive (adequate rainfall and lower weed density), yield losses occurred only when weeds reached 30 cm or more in corn and only in the untreated control in soybean. Corn and soybean yields were higher when planted in narrow rows in three of 4 yr but were more susceptible to earlyseason weed interference than corn and soybean in wide rows. Corn yield was affected more by weed interference than was soybean yield. The product of weed height by weed density, as the independent variable, resulted in the best linear fit for both corn and soybean yields. High weed densities increase the risk of yield loss and must be considered when determining the appropriate timing for total postemergence herbicide applications such as glyphosate. Sequential glyphosate applications in corn did not increase yield.