Sequential Applications Of Glufosinate Research Articles

Growth and fecundity of Palmer amaranth escaping glufosinate in soybean with and without grass competition

Abstract Field experiments were conducted at Clayton and Rocky Mount, North Carolina, during the summer of 2020 to determine the growth and fecundity of Palmer amaranth plants surviving glufosinate with and without grass competition in soybean. Glufosinate (590 g ai ha-1) was applied at early postemergence (5 cm Palmer amaranth height), mid-postemergence (7-10 cm), and late postemergence (>10 cm) and at orthogonal combinations of those timings. Non-treated Palmer amaranth was grown in weedy (i.e., intraspecific and grass competition), weed-free in-crop (WFIC), and weed-free fallow (WFNC) conditions for comparisons. No Palmer amaranth plants survived the sequential glufosinate applications and control decreased as the plants were treated at a larger size for both experiments. The apical and circumference growth rate of Palmer amaranth surviving glufosinate was reduced by more than 44% when compared to the WFNC Palmer amaranth. The biomass of Palmer amaranth plants surviving glufosinate was reduced by more than 87% when compared to the WFNC Palmer amaranth. The fecundity of Palmer amaranth surviving glufosinate was reduced by more than 70% when compared to WFNC Palmer amaranth. Palmer amaranth surviving glufosinate were as fecund as the WFIC Palmer amaranth in both experiments for soybean. The results prove that despite the significant vegetative growth rate decrease of Palmer amaranth surviving glufosinate, plants can be fecund as non-treated plants in soybean. The trends of growth and fecundity of Palmer amaranth surviving glufosinate with and without grass competition were similar. These results suggest that glufosinate-treated grass weeds may not reduce the growth or fecundity of Palmer amaranth surviving glufosinate.

Control of giant ragweed (Ambrosia trifida) in mesotrione-resistant soybean

Abstract Preemergence applications of mesotrione, an herbicide that inhibits 4-hydroxyphenolpyruvate dioxygenase (HPPD), have recently gained regulatory approval in soybean varieties with appropriate traits. Giant ragweed is an extremely competitive broadleaf weed, and biotypes resistant to acetolactate synthase inhibitors (ALS-R) can be particularly difficult to manage with soil-residual herbicides in soybean production. This study investigated control of giant ragweed from preemergence applications of cloransulam (32 g ai ha–1), metribuzin (315 g ai ha–1), and S-metolachlor (1,600 g ai ha–1) in a factorial design with and without mesotrione (177 g ai ha–1) at two different sites over 2 yr. Treatments with mesotrione were also compared with two commercial premix products: sulfentrazone (283 g ai ha–1) and cloransulam (37 g ai ha–1), and chlorimuron (19 g ai ha–1), flumioxazin (69 g ai ha–1), and pyroxasulfone (87 g ai ha–1). At 42 d after planting, control and biomass reduction of giant ragweed were greater in treatments with mesotrione than any treatment without mesotrione. Giant ragweed biomass was reduced by 84% in treatments with mesotrione, whereas treatments without mesotrione did not reduce biomass relative to the nontreated. Following these preemergence applications, sequential herbicide treatments utilizing postemergence applications of glufosinate (655 g ai ha–1) plus fomesafen (266 g ai ha–1) and S-metolachlor (1,217 g ai ha–1) resulted in at least 97% control of giant ragweed at 42 d after planting, which was greater than sequential applications of glufosinate alone in 3 of 4 site-years. Preemergence applications of mesotrione can be an impactful addition to soybean herbicide programs designed to manage giant ragweed, with the potential to improve weed control and delay the onset of herbicide resistance by providing an additional effective herbicide site of action.

Managing Palmer Amaranth (Amaranthus palmeri) with Sequential Applications of Glufosinate and 2,4-D

Aims: Determine the influence of sequential spray order and role of glufosinate when used in a system with 2,4-D to control Palmer amaranth at two different growth stages.
 Study Design: Randomized complete block design with three replications.
 Place and Duration of Study: A fallow, non-crop field at the Texas A&M AgriLife Research and Extension Center, Lubbock, Texas, during the 2018 and 2019 growing seasons.
 Methodology: Herbicides were applied to 7 to 15 cm and 25 to 30 cm Palmer amaranth with a handheld 1.93m CO2-pressurized backpack calibrated to deliver 140 L ha-1 at 207 kPa. Palmer amaranth control was visually estimated on a scale of 0 (no control) to 100% (complete control) relative to the nontreated control. Palmer amaranth biomass and density were collected 43 and 36 days after the last sequential application for 7 to 15 cm and 25 to 30 cm Palmer amaranth in 2019. Palmer amaranth control, biomass, and density were subjected to analysis of variance and means were separated using Fisher’s Protected LSD at P=.05.
 Results: 2,4-D choline + glyphosate followed by glufosinate provided the greatest level of Palmer amaranth control for both sizes of Palmer amaranth. Overall, Palmer amaranth control was not influenced by sequential application timing. Biomass and density were not significantly different among treatments.
 Conclusion: Sequential application order of glufosinate and 2,4-D was not an important factor for Palmer amaranth control. However, due to 2,4-D label restrictions, applying 2,4-D choline + glyphosate followed by glufosinate may be the best option for maximum efficacy.

Timing and Application Rate for Sequential Applications of Glufosinate are Critical for Maximizing Control of Annual Weeds in LibertyLink® Soybean

Preserving the utility of glufosinate in both LibertyLink soybean and other glufosinate-resistant crops is critical for managing herbicide-resistant weeds. An experiment with a two-factor factorial arrangement was conducted at the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, in 2015, 2016, and 2017 to evaluate the efficacy of glufosinate in single and sequential applications at various rates on 8–32 cm tall Palmer amaranth, barnyardgrass, and broadleaf signalgrass. Herbicide treatments consisted of glufosinate applied at 454, 595, 738, and 882 g ai ha−1 (Factor 1) with either no sequential application or a sequential application occurring 7, 10, 14, or 21 days after the initial application (DAI) (Factor 2). For treatments that contained a sequential application, the same rate used in the initial application (e.g., 451 g ai ha−1) was also used in the sequential. Regardless of species and rate, sequential applications were always superior to single applications. Palmer amaranth control 3 weeks after the final treatment (WAF) was 8% greater when the sequential application occurred 10 DAI compared to 21 DAI, averaged over glufosinate rates. When at least 595 g ai ha−1 glufosinate was used in a treatment, no differences between the 7-, 10-, 14-, and 21-day sequential application intervals were observed for barnyardgrass or broadleaf signalgrass control, 3 WAF. Soybean yields were greater when the glufosinate applications occurred 7 or 10 d apart compared to 21 d, averaged over glufosinate rates. When large weeds are present in the field, these data suggest that glufosinate should be applied sequentially with a 7- to 14-day interval between applications. If sequential applications of glufosinate are used in combination with a comprehensive weed control management program, the value of the LibertyLink technology should be preserved by mitigating the risk of glufosinate resistance.

Interval between sequential glufosinate applications influences weed control in cotton

AbstractDicamba and 2,4-D systems control many problematic weeds; however, drift to susceptible crops can be a concern in diverse production areas. Glufosinate-based systems are an alternative, but current recommended rates of glufosinate can result in variable control. Research was conducted in 2017 and 2018 to investigate the optimum time interval between sequential glufosinate applications and determine if the addition of glyphosate with glufosinate is beneficial for controlling Palmer amaranth and annual grasses in cotton. The interval between sequential applications (1, 3, 5, 7, 10, or 14 d or no second spray) was the whole plot and herbicide option (glufosinate or glufosinate plus glyphosate) was the subplot. Combined over herbicides, Palmer amaranth 15- to 20-cm tall (at four locations) was controlled 98% to 99% with sequential intervals of 1 to 7 d compared with 70% to 88% with intervals of 10 or 14 d. Lowest biomass weight and population densities were noted with 1- to 7-d intervals. Large crabgrass 15- to 20-cm tall (at five locations) was controlled 93% to 98% with glufosinate applications 3- to 7-d apart as compared with 76% to 81% with applications 10- to 14-d apart. Lowest biomass weights were observed with 1- to 7-d intervals. When glufosinate controlled grass less than 93%, adding glyphosate was beneficial. Neither interval between sequential applications nor herbicide option influenced cotton yield. Shorter time intervals between sequential application and including glyphosate can improve the effectiveness of a glufosinate-based system in managing Palmer amaranth and large crabgrass.

Barnyardgrass (Echinochloa crus-galli) Control as Affected by Application Timing of Glufosinate Applied Alone or Mixed with Graminicides

AbstractField and greenhouse studies were conducted to evaluate the antagonism potential of glufosinate applied sequentially or mixed with graminicides on barnyardgrass control. Applications of glufosinate alone provided variable control throughout the growing season in both field and greenhouse experiments. In the field, barnyardgrass control was not adversely affected by glufosinate- and clethodim-mix applications or sequential applications of glufosinate before or after clethodim. Soybean yield was not affected by application timing or clethodim rate, with yield ranging from 1,748 to 2,733 kg ha−1. In the greenhouse, glufosinate applied 1 and 3 d before graminicides generally reduced barnyardgrass control compared with the graminicides applied alone. The response with quizalofop-P was not as dramatic as with the other graminicides. Although significant visual barnyardgrass control differences were detected due to application timing of glufosinate, barnyardgrass biomass with fluazifop-P and quizalofop-P did not differ between the application timings of glufosinate. However, glufosinate applied 1 and 3 d before clethodim had significantly greater biomass compared with glufosinate applied 1 and 3 d after clethodim. The differences in environmental conditions and growth stages at the time of application may have contributed to barnyardgrass control response differences between the field and greenhouse experiments. Although barnyardgrass control in the field was not affected by glufosinate application timing, data from the greenhouse indicate potential exists for reduced control if glufosinate is applied 1 or 3 d before graminicides.

LibertyLink®, WideStrike® and XtendFlex® Tolerance to Late Postemergence Applications of Glufosinate and S-Metolachlor

Glufosinate remains an important postemergence (POST) herbicide for controlling glyphosate-resistant Amaranthus palmeri (S. Wats) in auxin-tolerant trait systems. Although visual injury from glufosinate applications to WideStrike cultivars is expected, concerns have been raised on the visual injury noted in XtendFlex cultivars, particularly with sequential late-POST glufosinate applications or when S-metolachlor is tank-mixed with glufosinate. Field trials were established in Jackson, TN during 2015 and 2017 and in Huntersville, TN during 2016. Herbicide treatments included an untreated; one, two, and three sequential applications of glufosinate; and glufosinate + S-metolachlor followed by (FB) glufosinate FB glufosinate + S-metolachlor. Applications began 40 days after planting and sequential applications were made every 10 to 14 days. Cultivars included DP 1522 B2XF (DeltaPine, Bayer CropScience, St. Louis, MO), PHY 333 WRF (Phytogen, Corteva Agriscience, Indianapolis, IN), and ST 4946 GLB2 (Stoneville, BASF Corp., Florham Park, NJ). Visual injury ratings varied across timing, treatment, cultivar, and site-year. Three sequential applications of glufosinate with two applications of S-metolachlor caused 7 to 20%, 2 to 15%, and 1 to 8% injury 10 days after the last application in PHY 333 WRF, DP 1522 B2XF, and ST 4946 GLB2, respectively. Cultivar lint yield and fiber quality did not vary by herbicide treatment. Producers who apply glufosinate should expect increasing visual injury from LibertyLink to XtendFlex to WideStrike cultivars, with a sharp increase in visual injury from XtendFlex to WideStrike cultivars; however, sequential, labeled applications of glufosinate with or without two applications of S-metolachlor will likely not impact yields of LibertyLink, WideStrike, or XtendFlex cultivars.

Lack of effects of glyphosate and glufosinate on growth, mineral content, and yield of glyphosate- and glufosinate-resistant maize

ABSTRACTWhether herbicides used in transgenic, herbicide-resistant crops have negative effects on those crops has been controversial. Most all of the data on this topic has been on glyphosate-resistant (GR) soybean, with little information available on GR and glufosinate-resistant (GluR) maize. A GR plus GluR maize variety was evaluated in the greenhouse and the field for effects of glyphosate and glufosinate on growth, mineral content, and yield. Treatments were: 1) a herbicide-free control; 2) 980 g acid equivalent (a.e.) ha−1 glyphosate at 21 days after emergence (DAE); 3) 600 g active ingredient (a.i.) ha−1 glufosinate at 21 DAE; 4) sequential applications of glyphosate at 520 and 980 g a.e. ha−1 at 14 and 28 DAE, respectively; 5) sequential applications of glufosinate at 300 and 300 g a.i. ha−1 at 14 and 28 DAE, respectively; and 6) sequential application of glyphosate (980 g a.e. ha−1) and glufosinate (600 g a.i. ha−1) at 14 and 28 DAE, respectively. None of the herbicide treatments affected plant growth, yield, or content of N, P, K, Ca, Mg, S, Mn, Fe, Cu, or Zn in the greenhouse or field. In grain of field-grown plants, no glufosinate was found and glyphosate (0.12 ng g−1) was only found in the sequential glyphosate treatment.

Effect of Late-Season Herbicide Applications on Inflorescence and Seed Production of Glyphosate-Resistant Giant Ragweed (Ambrosia trifida)

Giant ragweed is one of the most competitive annual broadleaf weeds in corn and soybean crop production systems in the United States and eastern Canada. Management of giant ragweed has become difficult due to the evolution of resistance to glyphosate and/or acetolactate synthase (ALS)-inhibitor herbicides and giant ragweed’s ability to emerge late in the season, specifically in the eastern Corn Belt. Late-season herbicide application may reduce seed production of weed species; however, information is not available about late-season herbicide applications on giant ragweed seed production. The objective of this study was to evaluate the effect of single or sequential late-season applications of 2,4-D, dicamba, glyphosate, and glufosinate on inflorescence injury and seed production of glyphosate-resistant (GR) giant ragweed under greenhouse and field conditions (bare ground study). Single and sequential applications of glufosinate resulted in as much as 59 and 60% injury to giant ragweed inflorescence and as much as 78 and 75% reduction in seed production, respectively, under field and greenhouse conditions. In contrast, single or sequential applications of 2,4-D or dicamba resulted in ≥ 96% inflorescence injury and reduction in seed production in the field as well as in greenhouse studies. The results indicated that 2,4-D or dicamba are effective options for reducing seed production of glyphosate-resistant giant ragweed even if applied late in the season. Targeting weed seed production to decrease the soil seedbank will potentially be an effective strategy for an integrated management of GR giant ragweed.

Herbicide Programs for Control of Glyphosate-Resistant Volunteer Corn in Glufosinate-Resistant Soybean

Glyphosate-resistant (GR) volunteer corn is a significant problem weed in soybean grown in rotation with corn in the midwestern United States and eastern Canada. The objective of this study was to evaluate the efficacy of glufosinate applied in single or sequential applications compared with acetyl-coenzyme A carboxylase (ACCase) inhibitors applied alone or tank mixed with glufosinate for controlling GR volunteer corn in glufosinate-resistant soybean. At 15 d after early-POST (DAEP), ACCase inhibitors applied alone controlled volunteer corn 76 to 93% compared to 71 to 82% control when tank mixed with glufosinate. The expected volunteer corn control achieved by tank mixing ACCase inhibitors and glufosinate was greater than the glufosinate alone, indicating that glufosinate antagonized ACCase inhibitors at 15 DAEP, but not at later rating dates. ACCase inhibitors applied alone or tank mixed with glufosinate followed by late-POST glufosinate application controlled volunteer corn and green foxtail ≥ 97% at 30 DAEP. Single early-POST application of glufosinate controlled common waterhemp and volunteer corn 53 to 78%, and green foxtail 72 to 93% at 15 DAEP. Single as well as sequential glufosinate applications controlled green foxtail and volunteer corn greater than or equal to 90%, and common waterhemp greater than 85% at 75 d after late-POST (DALP). Contrast analysis suggested that glufosinate applied sequentially provided greater control of volunteer corn at 15 and 75 DALP compared to a single application. Similar results were reflected in volunteer corn density and biomass at 75 DALP. Volunteer corn interference did not affect soybean yield, partly because of extreme weather conditions (hail and high winds) in both years of this study.

Herbicide Programs for Controlling Glyphosate-Resistant Johnsongrass (Sorghum halepense) in Glufosinate-Resistant Soybean

Three field experiments were conducted in 2010 and 2012 in a soybean production field near West Memphis, AR, containing glyphosate-resistant johnsongrass. The goal of this research was to develop effective herbicide programs for glyphosate-resistant johnsongrass in glufosinate-resistant soybean. Control of the resistant johnsongrass was greater with glufosinate at 590 and 740 g ai ha−1than at 450 g ha−1. Sequential glufosinate applications were more effective than a single application, irrespective of rate. A PRE application of flumioxazin at 71 g ai ha−1immediately after planting provided no more than 26% johnsongrass control 6 wk after soybean emergence (WAE). The addition of clethodim at 136 g ai ha−1to sequential applications of glufosinate at 450 g ha−1improved control over sequentially applied glufosinate alone. Herbicide programs containing imazethapyr or imazamox in combination with glufosinate followed by clethodim plus glufosinate controlled johnsongrass at least 94% at 10 WAE and provided three distinct mechanisms of action, a highly effective resistance management strategy. Results from this research indicate that a high level of glyphosate-resistant johnsongrass control can be achieved through the use of several herbicide options in glufosinate-resistant soybean.

Management of Palmer Amaranth (Amaranthus palmeri) in Glufosinate-Resistant Soybean (Glycine max) with Sequential Applications of Herbicides

Palmer amaranth (Amaranthus palmeri S. Wats.) is one of the most difficult weeds to control in soybean (Glycine max (L.) Merr.) in North Carolina. Research was conducted during 2010 and 2011 to determine if Palmer amaranth control and soybean yield were affected by soybean plant population and combinations of preemergence (PRE) herbicides followed by a single application of glufosinate postemergence (POST) versus multiple applications of glufosinate POST. Palmer amaranth was controlled more and soybean yield was greater when soybean was established at 483,000 plants ha−1 in 3 of 4 experiments compared with soybean at 178,000 plants ha−1 irrespective of herbicide treatments. In separate experiments, application of PRE herbicides followed by POST application of glufosinate or multiple POST applications of glufosinate provided variable Palmer amaranth control, although combinations of PRE and POST herbicides controlled Palmer amaranth the most and provided the greatest soybean yield. In 1 of 3 experiments, sequential applications of glufosinate were more effective than a single application. Yield was higher in 2 of 3 experiments when glufosinate was applied irrespective of timing of application when compared with the nontreated control. In the experiment where glufosinate was applied at various POST timings, multiple applications of the herbicide provided the best control and the greatest yield compared with single applications.

Impact of Injury from Late Season Sequential Glufosinate Applications on Sugarbeet Yield

Bluehost - Top rated web hosting provider - Free 1 click installs For blogs, shopping carts, and more. Get a free domain name, real NON-outsourced 24/7 support, and superior speed. web hosting provider php hosting cheap web hosting, Web hosting, domain names, front page hosting, email hosting. We offer affordable hosting, web hosting provider business web hosting, ecommerce hosting, unix hosting. Phone support available, Free Domain, and Free Setup.

Influence of Glyphosate and Glufosinate on Weed Control and Sugarbeet (Beta vulgaris) Yield in Herbicide-Tolerant Sugarbeet1

Field trials were conducted in 1999 and 2000 to determine the influence of weed size and the number of glyphosate or glufosinate applications on weed control and sugarbeet yield. Glyphosate at 840 g/ha or glufosinate at 390 g/ha was applied one, two, or three times, beginning when the average weed height was 3, 10, 15, or 25 cm. Two sequential applications of glyphosate applied to 10-cm weeds or three sequential applications of glufosinate applied to 3-cm weeds provided weed control comparable to three sequential applications of desmedipham plus phenmedipham plus triflusulfuron plus clopyralid. Weed control and sugarbeet root yield were optimal for two postemergence applications of glyphosate and for three applications of glufosinate. Glyphosate provided greater control of redroot pigweed and common lambsquarters than glufosinate. Sugarbeet sucrose yield with both glyphosate and glufosinate weed control programs was nearly 10,000 kg/ha. Compared with two sequential applications of glyphosate, sucrose yiel...

Tolerance of transformed cotton to glufosinate

Field experiments from 1997 to 1999 examined cotton cv. ‘Coker 312’ that was genetically transformed to tolerate glufosinate. None of the glufosinate treatments caused visible injury to the glufosinate-tolerant cotton, but treatments were lethal to nontransformed or nonexpressing cotton. No glufosinate treatment adversely affected plant height at maturity, total number of nodes, bolls per plant, or boll positions. Glufosinate applications of 0.6 kg ha−1 made at eight stages of growth, ranging from cotyledon stage to 50% open boll, did not adversely affect yield or fiber quality as measured by micronaire or fiber length and strength. Sequential glufosinate applications up to four stages of growth from the zero- to one-leaf stage to the 14- to 15-leaf stage or individual glufosinate applications at 3.3 kg ha−1 made at the two- to three-leaf stage of growth also did not adversely affect yield or fiber quality. Overall yields in these studies were low relative to normal Texas Southern High Plains cotton yield because these studies were conducted using a Coker 312 parental line, which is generally a poor performer in this region. This research indicated that the transformation events for glufosinate tolerance in cotton were successful and the glufosinate-tolerance gene was expressed throughout the growing season. Transformation and field testing of other cotton varieties are needed to improve varietal performance on the Texas Southern High Plains.

Comparison of Weed Management Systems in Narrow-Row, Glyphosate- and Glufosinate-Resistant Soybean (Glycine max)1

Field experiments were conducted near DeKalb and Urbana, IL, and Columbia, MO, in 1997 and 1998 to evaluate weed management systems in glyphosate- and glufosinate-resistant soybean planted in 18-cm rows. Overall weed control was improved to a greater extent when the rate of glufosinate was increased from 300 to 400 g ai/ha than when the rate of glyphosate increased from 630 to 840 g ae/ha. Sequential applications of glufosinate improved control over single applications, whereas sequential treatments of glyphosate generally provided no advantages over single applications. When averaged across all weed species in these trials, the systems that provided 95% or higher average control were sequential applications of glufosinate, sequential applications of glyphosate, and clomazone followed by (fb) glyphosate. Single applications of glufosinate provided somewhat variable control of giant foxtail, common lambsquarters, ragweed, and common cocklebur similar to that observed with pendimethalin fb imazethapyr. The addition of fomesafen to glufosinate did not improve control of any of the weeds in this study with the exception of velvetleaf at DeKalb. The addition of clomazone to glufosinate treatments resulted in slightly better giant foxtail and velvetleaf control. Single applications of glyphosate provided somewhat variable control of giant ragweed at DeKalb in 1997 and ivyleaf morningglory and common cocklebur control at Columbia. The addition of fomesafen to glyphosate provided an increase in ivyleaf morningglory and common cocklebur control at Columbia but did not improve control of any other species. The addition of clomazone to glyphosate-based programs resulted in slightly higher velvetleaf, common cocklebur, and ivyleaf morningglory control. In the glyphosate-based herbicide programs there were no substantial differences in relative yield, with all programs protecting over 95% of soybean yield. Glufosinate-based programs were effective in protecting 85 to 92% of soybean yield.Nomenclature: Clomazone; fomesafen; glyphosate; glufosinate; imazethapyr; pendimethalin; common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; giant foxtail; Setaria faberi Herrm. # SETFA; giant ragweed, Ambrosia trifida L. # AMBTR; ivyleaf morningglory, Ipomoea hederacea L. Jacq. # IPOHE; velvetleaf, Abutilon theophrasti Medic. # ABUTH; soybean, Glycine max (L.) Merr.Abbreviations: EPOST, early postemergence; fb, followed by; LPOST, late postemergence, POST, postemergence; PRE, preemergence; UAN, 28% urea ammonium nitrate.

Economics of Weed Management in Glufosinate-Resistant Corn (Zea maysL.)1

Abstract: Field experiments were conducted in 1997 and 1998 near Columbia and Novelty, MO, and at Urbana, IL, to evaluate corn injury, weed control, corn yield, and estimated economic returns with weed management programs in glufosinate-resistant corn. Herbicide programs included acetochlor preemergence (PRE) followed by glufosinate alone or with atrazine postemergence (POST) and total POST programs consisting of single and sequential applications of glufosinate alone or tank mixed with acetochlor, atrazine, or acetochlor plus atrazine. Metolachlor PRE followed by dicamba plus atrazine early POST (EPOST) and metolachlor plus atrazine PRE were included for comparison. In the total POST treatments, mid-POST applications controlled shattercane and common cocklebur better than EPOST applications. However, yield reductions as high as 23% occurred because of early-season weed interference, although weeds were controlled later in the season. Applying atrazine with glufosinate generally increased control of giant...

Evaluation of Glufosinate-Resistant Corn (Zea mays) and Glufosinate: Efficacy on Annual Weeds

Field studies were conducted in 1996 and 1997 at Belleville and Pawnee, IL, to evaluate single and sequential applications of glufosinate on tolerance of glufosinate-resistant corn and annual weed control. Glufosinate caused 0 to 13% corn injury 7 days after treatment (DAT) and 0 to 6% corn injury 28 DAT. Injury was characterized as stunting with glufosinate. Glufosinate at 400 to 1,200 g ai/ha did not reduce final corn height or grain yield. At Pawnee in both years and at Belleville in 1996, a single application of glufosinate at 400 g/ha controlled giant foxtail, velvetleaf, ivyleaf morningglory, and common lambsquarters 85 to 100%. At Belleville in 1997, sequential applications of glufosinate provided greater weed control (87 to 100%) than a single application (0 to 63%) because of weed emergence after application. Weed control with a single application of glufosinate or with nicosulfuron plus bromoxynil was similar at both locations. Height and grain yield of glufosinate-resistant corn were not different from that of glufosinate-susceptible corn (isoline of glufosinate-resistant corn).

Efficacy and Crop Response to Glufosinate-Based Weed Management in PAT-Transformed Sweet Corn (Zea mays)

Field studies were conducted at Arlington, WI, in 1996 and 1997 and at Georgetown, DE, and LeSueur, MN, in 1997 to determine weed control efficacy, crop injury, and yield response of PAT-transformed sweet corn to glufosinate-based weed management. Sequential applications of glufosinate 10 to 18 d apart at 0.4 and 0.3 kg ai/ha controlled common lambsquarters, common ragweed, velvetleaf, wild-proso millet, and fall panicum 90% or better at all locations. Weed control varied little among 0.3, 0.4, or 0.3 and 0.3 (sequential) kg/ha glufosinate rates. Glufosinate applied alone, with, or following atrazine controlled velvetleaf 90% or greater but was less consistent on common ragweed and common lambsquarters (73 to 100%). Atrazine plus metolachlor applied preemergence (PRE) and glufosinate applied alone postemergence (POST) provided inconsistent wild-proso millet and fall panicum control (43 to 99%). Metolachlor followed by glufosinate improved consistency of grass control (> 76%). Glufosinate followed by cultivation provided 80% or greater control of velvetleaf and wild-proso millet. Glufosinate did not injure or delay maturity of PAT-transformed sweet corn. Sweet corn treated with glufosinate resulted in yields greater than or equal to the sweet corn that was hand-weeded or received a standard herbicide treatment.