Glufosinate Treatments Research Articles

Growth and fecundity of Palmer amaranth escaping glufosinate in cotton 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 that survived glufosinate with and without grass competition in cotton. Glufosinate (590 g ai ha-1) was applied to Palmer amaranth early postemergence (5 cm tall), mid postemergence (7 to 10 cm tall), and late postemergence (>10 cm tall) and at orthogonal combinations of those timings. Non-treated Palmer amaranth was grown in weedy, weed-free in-crop (WFIC) and weed-free fallow (WFNC) conditions for comparisons. Palmer amaranth control decreased as larger plants were treated; no plants survived the sequential glufosinate applications in both experiments. The apical and circumferential growth of Palmer amaranth surviving glufosinate treatments was reduced by more than 44% compared to the WFIC and WFNC Palmer amaranth in both experiments. The biomass of Palmer amaranth plants surviving glufosinate was reduced by more than 62% when compared with the WFIC and WFNC in all experiments. The fecundity of Palmer amaranth surviving glufosinate treatments was reduced by more than 73% compared to WFNC Palmer amaranth in all experiments. Remarkably, the plants that survived glufosinate were fecund as WFIC plants only in the Grass Competition experiment. The results prove that despite decreased vegetative growth of Palmer amaranth surviving glufosinate treatment, plants remain fecund and can be fecund as non-treated plants in cotton. These results suggest that a glufosinate-treated grass weed may not have a significant interspecific competition effect on Palmer amaranth that survives glufosinate. Glufosinate should be applied to 5 to 7 cm Palmer amaranth to cease vegetative and reproductive capacities.

Multiple herbicide-resistant kochia (Bassia scoparia) control in glufosinate-resistant canola

Multiple herbicide-resistant kochia ( Bassia scoparia (L.) A.J. Scott) has grown in prevalence in the canola ( Brassica napus L.) production region of North America. Glufosinate-resistant canola facilitates kochia management since glufosinate-resistant kochia is not known to occur. Field experiments were conducted from 2013 to 2015 in five environments near Lethbridge and Coalhurst, Alberta, to identify herbicide strategies targeting acetolactate synthase inhibitor-resistant kochia with and without glyphosate resistance in glufosinate-resistant canola. Sequential glufosinate treatments (500 g ai ha−1) postemergence (POST) caused excellent (≥90%) kochia control and biomass reduction across environments. Preplant (PP) carfentrazone + sulfentrazone (9 + 105 g ai ha−1) alone or followed by (fb) POST glufosinate (9 + 27 fb 500 or 9 + 105 fb 500 g ai ha−1) resulted in excellent kochia control in all environments tested. PP carfentrazone + sulfentrazone (9 + 53 g ai ha−1) alone, and a single POST treatment with glufosinate (500 or 590 g ai ha−1) alone or preceded by fall-applied ethalfluralin (1100 fb 500 g ai ha−1) with or without PP carfentrazone (1100 fb 9 fb 500 g ai ha−1) caused ≥80% kochia control and biomass reduction in all environments tested. However, treatments containing PP carfentrazone + sulfentrazone caused unacceptable canola injury or yield loss in at least one environment. In conclusion, single or sequential treatments of glufosinate POST managed multiple herbicide-resistant kochia effectively in canola. Layering fall-applied/PP ethalfluralin and/or PP carfentrazone with glufosinate POST may help alleviate resistance selection pressure placed on glufosinate in canola.

Biological effects on Palmer amaranth surviving glufosinate

AbstractPalmer amaranth (Amaranthus palmeri S. Watson) is a difficult weed to manage due to competitive growth, fecundity, and evolved herbicide resistance. Limited information exist on the fecundity of vegetative stage Palmer amaranth surviving glufosinate applied at different timings. In addition, research has not investigated the germination or glufosinate susceptibility of the offspring from these surviving plants. Field experiments were conducted across three locations in 2019 to determine (a) the fecundity of Palmer amaranth plants surviving glufosinate applied at different vegetative growth stages, and (b) if the offspring from the surviving plants exhibited differential germination and susceptibility to glufosinate. Palmer amaranth was treated at three different vegetative sizes (5 cm, 7–10 cm, > 10 cm) and orthogonal combinations of these application timings. The application timings corresponded to early‐, mid‐ and late‐postemergence applications. Palmer amaranth plants surviving the mid‐, late‐, and the mid postemergence followed by late postemergence glufosinate application were fecund. Palmer amaranth plants surviving the mid postemergence followed by late postemergence application produced less seed than the plants surviving the mid postemergence and late postemergence application. Palmer amaranth was controlled with other glufosinate applications resulting in no seed production. Germination was affected across location and glufosinate treatments, but no clear trend/pattern was observed. The offspring from Palmer amaranth plants surviving glufosinate applications were controlled by all glufosinate rates tested. These experiments provide evidence that Palmer amaranth surviving glufosinate in the vegetative stages may remain fecund, but fecundity can vary with application timing. No measurable effect on the offspring germination or susceptibility to glufosinate was apparent.

The Effect of Nitrogen Rate on Vine Kill, Tuber Skinning Injury, Tuber Yield and Size Distribution, and Tuber Nutrients and Phytonutrients in Two Potato Cultivars Grown for Early Potato Production

Sixteen vine kill programs were tested on Bintje and Ciklamen potato cultivars grown for early potato production over a three year period near Paterson, Washington. Mechanical (flail chopping, flail chopping and undercutting), chemical (glufosinate, diquat, sulfuric acid, carfentrazone, pyraflufen-ethyl), and physical (flaming) vine kill methods, and sequential combinations of the three were effective in killing rapidly growing potato vines of Bintje and Ciklamen. Rolling and crimping did not kill vines as completely and more vine regrowth occurred than with most other methods tested. Tuber skinning injury was greatly reduced when harvesting at 4 weeks after initial vine kill than at 2 weeks. None of the vine kill programs were able to hasten skin set enough to allow tubers to be harvested at 2 weeks after initial vine kill without significant tuber skinning injury. Glufosinate treatments that were applied several days earlier than other initial vine kill treatments tended to average less skinning injury at the early harvest possibly due to more time elapsing between initial vine kill and harvest. Total tuber yield and size distribution were similar among most vine kill treatments, with the exception of the earlier applied glufosinate treatments, which tended to reduce total yield, but still yielded a similar mass of desired 25 to 35 mm diameter tubers. Tubers from vine-killed plots tended to average greater N, P, K, Fe, and Ca content than tubers from non-killed control plots of both cultivars. Tuber ascorbate levels were also greater in non-killed controls, whereas total phenolic content tended to be greatest in earlier-applied glufosinate treatments. Nonchemical vine kill methods, chemical vine kill methods, and combinations of the two were identified that killed vines well, had low skinning injury at the 4 week harvest, and yielded similar amounts of 25 to 35 mm diameter early potato tubers.

Evaluation of WideStrike Cotton Response to Repeated Applications of Glufosinate at Various Application Timings

Glyphosate-resistant (GR) weeds are most challenging for growers to control in cotton in the midsouth region of the United States. As a result, growers in these states are transitioning from a glyphosate-based system to a glufosinate-based system. A field study was conducted in 2010 and 2011 in Georgia, North Carolina, and Tennessee to determine the effect of repeated glufosinate applications to WideStrike cotton applied at various application timings. One to three glufosinate applications at 594 g ai ha−1were applied to cotton at the two-leaf, seven-leaf, bloom, or 2 wk after bloom stages. Visual estimates of crop injury were evaluated after each application, in addition to crop height, development, and yield. Crop injury after each glufosinate application typically ranged from 3 to 11%, with higher injury observed where multiple glufosinate applications were made. Crop height differences were noted after the bloom and 2 wk after bloom applications. Treatments that had one, two, or three glufosinate applications had reduced crop height when compared with the weed-free control. Node above cracked boll ratings also indicated that glufosinate treatments may have stressed the cotton. Ultimately, yield was reduced where three glufosinate treatments were applied to WideStrike cotton. In addition, one glufosinate application at the bloom stage or two glufosinate applications at the bloom and 2 wk after bloom stages reduced yield when compared with the weed-free control. Although it is a legal application, growers should use caution when applying glufosinate to WideStrike cotton because the manufacturer of glufosinate and the manufacturer of WideStrike cotton do not recommend this application. However, where GR Palmer amaranth is present, these applications may be necessary.

Glufosinate Safety in WideStrike® Acala Cotton

WideStrike® Acala cotton is a two-gene, in-plant trait that provides broad-spectrum and season-long control of lepidopteran insect pests, and the varieties available in California also have resistance to glyphosate. There have been indications that WideStrike cotton has some glufosinate tolerance as well, so the level of tolerance to glufosinate needed to be ascertained. A 2-yr (2008 and 2009) study was conducted in California to evaluate the potential crop injury caused by three different rates (0.59, 0.88, and 1.76 kg ai ha−1) of glufosinate–ammonium at four different growth stages (cotyledon, 2-node, 5- to 6-node, and 18- to 19-node stages) of WideStrike Acala cotton. The effects of these treatments on the cotton plants and yield were closely monitored. Glyphosate at 1.54 kg ae ha−1 was applied at all cotton growth stages as a standard application, and a nontreated control was included. The greatest level of injury (58%) was observed with the highest rate of glufosinate applied at both the cotyledon and the two-node stage of cotton. However, injury was less than 10% following glufosinate at 0.59 kg ha−1 applied at the 18- to 19-node stage. The level of injury increased with the higher application rate of glufosinate at all crop growth stages. In 2008 and 2009, the glufosinate treatments had no effect on cotton lint yield. Therefore, the study showed that glufosinate can be applied safely topically at 0.59 kg ha−1 at the cotyledon- to 2-node stage or as POST-directed spray between the 5- to 19-node stages. Although injury occurred at this rate, the plants recovered within 2 to 3 wk of the treatment. Increasing glufosinate rates beyond 0.59 kg ha−1 can increase the possibility of greater crop injury.

POST Control of Carolina Redroot (Lachnanthes caroliniana)

Greenhouse studies were conducted in 2012 in Raleigh, NC to determine Carolina redroot control by ten POST herbicides. Paraquat and glufosinate provided the greatest control 14 (73 and 64%, respectively) and 25 d (82 and 68%, respectively) after treatment (DAT), but control declined between 25 and 63 DAT (72 and 59%, respectively). Glyphosate provided minimal control 14 DAT (18%), and control increased from 14 to 25 DAT (46%) and 25 to 63 DAT (69%). Control of Carolina redroot roots and rhizomes (roots/rhizomes) was greatest in plants treated with paraquat (91%), glyphosate (88%), glufosinate (73%), hexazinone (62%), diuron (60%). Nontreated Carolina redroot shoot and root/rhizome dry weight were 8.3 and 7.6 g, respectively. Paraquat, glufosinate, glyphosate, and diuron reduced both shoot and root/rhizome dry weight (3.1 and 0.7 g, 5.1 and 2.7 g, 5.4 and 1.0, 5.7 and 1.6 g, respectively). Hexazinone reduced root/rhizome dry weight (2.7 g). Fomesafen reduced shoot dry weight (6.1 g), but did not reduce root/rhizome dry weight. Paraquat, glufosinate, glyphosate, hexazinone, diuron, and clopyralid treatments resulted in reduced incidence of Carolina redroot flowering and anthesis.

MINERALIZATION AND CORN RECOVERY OF 15NITROGEN FROM BLACK OATS RESIDUES TREATED WITH HERBICIDES

Nitrogen (N) mineralization from black oat residues (Avena strigosa), with or without previous application of herbicides, and its utilization by corn crop were investigated. The experiments were performed in a completely randomized setup, with three treatments and ten replicates. The treatments were: A) control - corn grown in soil with residues of black oats harvested without herbicide application; B) glyphosate - corn grown in soil with residues of glyphosate-desiccated black oat; and C) glufosinate - corn grown in soil with residues of black oat previously desiccated with glufosinate-ammonium. The remaining black oat residues on the soil surface were smaller in the control treatment than in glyphosate and glufosinate treatments. Black oat residues from the control treatment released 30% and 20% more carbon (C) and nitrogen (N), respectively, than from herbicide treatments. Microbial biomass carbon, total and mineral soil N arising from black oat residues were reduced by herbicide management. Black oat residues treated with glyphosate reduced corn total-N by 16%; however, dry mass yield was not affected by the treatments. Herbicide application on black oat reduced the total amount of residue-released nitrogen in the corn kernels, leaves and the whole plant. Net nitrogen mineralization from black oat residues is affected by the application of glyphosate or glufosinate-ammonium.

The pleiotropic effects of the bar gene and glufosinate on the Arabidopsis transcriptome

SummaryThe Arabidopsis transcriptome was studied using the Affymetrix Arabidopsis ATH1 GeneChip in wild‐type plants and glufosinate‐tolerant transgenic plants expressing the bialaphos resistance (bar) gene. Pleiotropic effects were specifically generated in the transcriptomes of transgenic plants by both the bar gene and glufosinate treatments. In the absence of glufosinate, four genes were differentially expressed in the transgenic lines and another 80 genes were differentially expressed in the presence of glufosinate, 29 of which were specific to transgenic plants. In contrast, the number of differentially expressed genes specific to wild‐type plants was 194 during the early response at 6 h of glufosinate treatment, and increased to 3711 during the late response at 48 h. Although the wild‐type plants undergo extensive transcriptional reprofiling in response to herbicide‐induced stress and, finally, plant death, the transgenic plants appear to activate other detoxification processes to offset the toxic effects of the residual herbicide or its derivatives. This study provides the first description of the pleiotropic effects of the bar gene and glufosinate on the plant transcriptome.

The pleiotropic effects of thebargene and glufosinate on theArabidopsistranscriptome

The Arabidopsis transcriptome was studied using the Affymetrix Arabidopsis ATH1 GeneChip in wild-type plants and glufosinate-tolerant transgenic plants expressing the bialaphos resistance (bar) gene. Pleiotropic effects were specifically generated in the transcriptomes of transgenic plants by both the bar gene and glufosinate treatments. In the absence of glufosinate, four genes were differentially expressed in the transgenic lines and another 80 genes were differentially expressed in the presence of glufosinate, 29 of which were specific to transgenic plants. In contrast, the number of differentially expressed genes specific to wild-type plants was 194 during the early response at 6 h of glufosinate treatment, and increased to 3711 during the late response at 48 h. Although the wild-type plants undergo extensive transcriptional reprofiling in response to herbicide-induced stress and, finally, plant death, the transgenic plants appear to activate other detoxification processes to offset the toxic effects of the residual herbicide or its derivatives. This study provides the first description of the pleiotropic effects of the bar gene and glufosinate on the plant transcriptome.

Weed control in conventional and herbicide tolerant winter oilseed rape (Brassica napus) grown in rotations with winter cereals in the UK

SummaryTwo winter oilseed rape (Brassica napus) cultivars, tolerant to glyphosate and glufosinate, were compared with a conventional cultivar at three sites over 4 years, in 3‐year crop rotations in the UK. The winter oilseed rape was grown in Years 1 and 4, with winter cereals, which received uniform herbicide treatments, in the intervening years. The second winter oilseed rape treatments were applied to randomised sub‐plots of the original plots. Weed densities were recorded in autumn and spring and weed biomass was measured in summer. At most sites, there was only one application of glufosinate or glyphosate, whereas two products were often used on the conventional variety. The timing of glyphosate and glufosinate application was, on average, 34 days later than that of the conventional broad‐leaved weed control treatments. Overall weed control, across all sites and years, was not statistically different between the conventional, glyphosate and glufosinate treatments. However, glyphosate achieved higher control of individual weed species more frequently than the other treatments. Glufosinate and the conventional treatments were similar in performance. The treatments in Year 1 sometimes affected weed populations in the subsequent cereal crops and, in rare instances, those in the rape in Year 4. Carry‐over effects were small after most treatments. In general, weed survival was greater in the oilseed rape crops, irrespective of the treatment, than it was in the intervening cereal crops.

Molecular Analysis, Cytogenetics and Fertility of Introgression Lines From Transgenic Wheat to Aegilops cylindrica Host

Natural hybridization and backcrossing between Aegilops cylindrica and Triticum aestivum can lead to introgression of wheat DNA into the wild species. Hybrids between Ae. cylindrica and wheat lines bearing herbicide resistance (bar), reporter (gus), fungal disease resistance (kp4), and increased insect tolerance (gna) transgenes were produced by pollination of emasculated Ae. cylindrica plants. F1 hybrids were backcrossed to Ae. cylindrica under open-pollination conditions, and first backcrosses were selfed using pollen bags. Female fertility of F1 ranged from 0.03 to 0.6%. Eighteen percent of the sown BC1s germinated and flowered. Chromosome numbers ranged from 30 to 84 and several of the plants bore wheat-specific sequence-characterized amplified regions (SCARs) and the bar gene. Self fertility in two BC1 plants was 0.16 and 5.21%, and the others were completely self-sterile. Among 19 BC1S1 individuals one plant was transgenic, had 43 chromosomes, contained the bar gene, and survived glufosinate treatments. The other BC1S1 plants had between 28 and 31 chromosomes, and several of them carried SCARs specific to wheat A and D genomes. Fertility of these plants was higher under open-pollination conditions than by selfing and did not necessarily correlate with even or euploid chromosome number. Some individuals having supernumerary wheat chromosomes recovered full fertility.

Glifosato e glufosinato como agentes seletivos para transformação genética de maracujá amarelo (Passiflora edulis f. Flavicarpa deg.)

The yellow passion fruit is one of the most interesting economic species of Passifloraceae family. The biotechnology tools are useful to solve some problems that affect the productive potencial of this specie, like fungal and bacterial diseases, and the creation of more productivity varieties. In this context an experiment of yellow passion fruit was corried out to evaluate the glyphosate and gluphosinato herbicides as selective agents for genetic transformation. The culture medium used was Murashige & Skoog (1962) supplemented with B5 vitamin and organic complex, 30 g.L-1 sucrose, 100 mg.L-1 inositol, 1 mg.L-1 6– benzilaminopurina, solidified with 2,6 g.L-1 Phytagel. The experimental design was entire occasional and the bud regeneration and rooting formation experiments were evaluated. The glyphosate concentrations used in experiments of bud regeneration were: 0; 0,2; 0,4; 0,6; 0,8; 1,0 mg.L-1, for rooting experiments: 0; 0,05; 0,1; 0,15; 0,20; 0,30; 0,40 mg.L-1. The glufosinate treatments for bud regeneration were: 0,0; 0,2; 0,4; 0,6; 0,8 mg.L-1 and for rooting experiments: 0,0; 0,1; 0,15; 0,20; 0,25 mg.L-1. Number of explant with shoots and number of shoots per explant were evaluated in the experiment of caulogenesis. For rooting evaluation: number of rooted apexes, root size, primary root number and root fresh weight. Both herbicides glyphosate and glufosinate were efficient in the inhibition of the bud regeneration to a low concentration (0,785 mg.L-1 e 0,768mg.L-1 respectively), as well as in the inhibition of rooting (0,404 mg.L-1 e 0,249 mg.L-1 respectively). That allows the recommendation of those herbicides as selective agents in tissue culture of passion fruit for works of genetic transfer.

Yield of Glufosinate-Resistant Sugarbeet in Response to Postemergence Glufosinate

ha· Experiments were conducted to determine the effect of glu­ fosmate rate and herbicide starting time on glufosinate­ resistant sugarbeet (Beta vulgaris L) injury and yield. Sequential glnfosinate applications starting two weeks or later and ending five to seven weeks after the sugarbeet cotyledon stage caused significant visible sugarbeet injury while injury was minimal with treatments starting at the cotyledon stage or one week later. Sugarbeet yield declined when sequential glufosinate treatments were applied at weekly intervals and the first treatment was delayed until f~ur weeks or one week after the sugarbeet cotyledon stage in 1998 and 1999, respectively. Sugarbeet yield loss may be attributed to sugarbeet injury or prolonged weed competi­ tion prior to the first sequential glufosinate application. As the glufosinate rate increased from 0.2 to 0.4 and 0.8 kg l , glufosinate had to be applied to younger sugarbeet to a-void sugarbeet injury. Glufosinate-resistant sugarbeet treat-ed three times with glufosinate yielded less in 1998 than sugarbeet that was hand weeded at the same time pat­ tern as glufosinate was applied. Similar results were found in 1999 at one location, but yield from glufosinate-treated and hand-weeded plots did not differ at two locations, despite the significant herbicide­ induced sugarbeet injury observed seven days after the last treatment. Glufosinate, regardless of rate, can safely be applied to sugarbeet starting at the cotyledon stage or one week thereafter without causing yield loss.

Glufosinate Does Not Affect Floral Morphology and Pollen Viability in Glufosinate-Resistant Cotton

Studies were conducted to determine whether glufosinate treatments to glufosinate-resistant cotton caused changes in floral morphology, pollen viability, and seed set. Four glufosinate treatments were included: (1) glufosinate applied postemergence over the top (POST) at the four-leaf stage, (2) glufosinate applied POST at the eight-leaf stage, (3) the first two treatments sequentially, and (4) a POST application at the four-leaf stage followed by (fb) a postemergence-directed stem application (PDS) at the eight-leaf stage. Glufosinate was consistently applied at 0.49 kg ai/ha. A nontreated control was included. Glufosinate treatments did not affect stigma height, length of the staminal column, or pollen viability. However, the distance from the top anther to the tip of the stigma was less in plants treated with an eight-leaf POST treatment than in nontreated plants, although this difference is not likely to influence pollen deposition because in both cases anthers reached above the stigma tip. Plants receiving four-leaf POST fb eight-leaf PDS treatment with glufosinate had eight seeds per boll less than nontreated plants; however, the more rigorous four-leaf POST fb eight-leaf POST treatment did not differ from the nontreated in seeds per boll.

Glufosinate Rates, Timings, and Additives for Weed Control in Glufosinate-Resistant Sugarbeet

Two experiments were conducted to evaluate weed control with glufosinate in glufosinate-resistant sugarbeet. The first experiment evaluated glufosinate rate, application timing, and combinations with ammonium sulfate (AMS). The second experiment examined glufosinate alone and in combination with postemergence (POST) or preplant incorporated (PPI) ethofumesate. In the first experiment in 1998, increasing glufosinate rate improved common lambsquarters ~ � control and redroot pigweed control was greater when I � glufosinate was initially applied mid-post (MP) compared to early-post (EP). In 1999, increasing glufosinate rate, beginning treatment at the EP application timing, and the addition ofAMS, increased redroot pigweed control. Barnyardgrass control also was improved with the higher glufosinate rate and with the addition of AMS. Sugarbeet yield in 1998 was not significantly affected by glufosinate treatments. In 1999, the addition of AMS to low glufosinate rates and the addition of AMS to treatments applied beginning MP increased sugarbeet yield. In the second experiment, three applications of glufosinate and two applications of glufosinate following PPI ethofumesate resulted in weed control equal to a standard herbicide program consisting ofPPI ethofumesate followed by a premix of ethofumesate, desmedipham, and phenmedipham (1: 1: 1

Glufosinate Efficacy on Amaranthus Species in Glufosinate-Resistant Soybean (Glycine max)1

Field studies were conducted in 1998 and 1999 to evaluate the efficacy of glufosinate on Palmer amaranth, redroot pigweed, and common waterhemp at different growth stages in soybean planted at early, normal, and late dates. At 2, 4, and 8 wk after treatment, common waterhemp control was greater than Palmer amaranth and redroot pigweed control with single glufosinate applications of 410 g ai/ha at 2- to 5-, 7- to 10-, or 15- to 18-cm Amaranthus height or with two sequential applications of 293 g/ha at 2- to 5-cm height and 2 wk later. Only the sequential applications of 410 and 293 g/ha resulted in more than 80% control of Palmer amaranth and redroot pigweed, but all five treatments controlled common waterhemp more than 80%. All glufosinate treatments reduced the dry weight of all Amaranthus species by more than 65%. However, the sequential applications resulted in the greatest dry weight reductions.Nomenclature: Glufosinate; common waterhemp, Amaranthus rudis Sauer #3 AMATA; Palmer amaranth, Amaranthus palmeri S.Wats. # AMAPA; redroot pigweed, Amaranthus retroflexus L. # AMARE; soybean, Glycine max (L.) Merr.Additional index words: Environmental conditions, herbicide-tolerant soybean, postemergence herbicide.Abbreviations: ALS, Acetolactate synthase (EC 4.1.3.18); OM, organic matter; RH, relative humidity; WAT, weeks after treatment.

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.

Highbush Blackberry (Rubus argutus) Control in Bahiagrass (Paspalum notatum)

A 3-yr study investigated highbush blackberry control in bahiagrass turf using selective herbicides. Triclopyr applied alone at ≤ 0.56 kg/ha and in combination with other herbicides provided best (75 to 95%) control for up to 52 wk after treatment with minimal damage to bahiagrass turf. Triclopyr formulations (3A vs 4EC) provided similar highbush blackberry control and bahiagrass tolerance. The addition of either 2,4-D, dicamba, hexazinone, or sulfometuron to triclopyr provided slightly better blackberry control, but increased bahiagrass turf damage. Fluroxypyr applied at 0.14 to 0.28 kg/ha provided 60 to 80% control of highbush blackberry 12 WAT. Glyphosate and glufosinate treatments provided unacceptable highbush blackberry control and/or unacceptable bahiagrass turf injury. The addition of oxadiazon for residual control of subsequent highbush blackberry emergence was ineffective.