2,4-dichlorophenoxyacetic acid (2,4-D) is an analogue compound to the plant hormone indole-3-acetic acid (IAA), which is used either as a growth-promoting substance or as a herbicide, depending on its concentration. In this work, the effect of 2,4-D on the growth and ROS metabolism of pea (Pisum sativum L.) leaves is reported. The herbicide considerably reduced the plant growth and negatively influenced several physiological parameters in a dose-dependent manner. At structural level, damage of the mesophyll cells and the enlargement and dilation of thylakoids were observed in 2,4-D-treated plants. 2,4-D notably affected xanthine oxidase and superoxide dismutase activities, as well as the activity and transcript levels of the ascorbate–glutathione cycle enzymes, ascorbate peroxidase, monodehydroascorbate reductase, and glutathione reductase. Furthermore, in herbicide-treated plants, an increase in the H2O2 production, levels of lipid peroxidation, endopeptidase activity and oxidatively modified proteins took place. Results obtained showed that an overproduction of superoxide radicals (O2−) and hydrogen peroxide (H2O2) could take place in plants treated with 2,4-D, thus contributing to the generation of oxidative stress, with the concomitant degradation of proteins. A model of the role of ROS-mediated enzymatic systems in the oxidative mode of action of 2,4-D and other auxinic herbicides is proposed.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2004.01219.x

Reactive oxygen species‐mediated enzymatic systems involved in the oxidative action of 2,4‐dichlorophenoxyacetic acid*

Phenoxyacetic acids: separation and quantitative determination

Studies were conducted in 2002 and 2003 on a golf course fairway in New Jersey to compare spring, summer, and fall treatments of bispyribac-sodium for annual bluegrass control and creeping bentgrass tolerance. Single applications at 74, 111, or 148 g ai/ha were applied in May, August, or October. Split applications of 37 followed by (fb) 37 or 74 fb 74 g/ha applied 3 wk apart were also evaluated. Summer-applied bispyribac-sodium did not reduce bentgrass quality, whereas spring and fall treatments reduced turf quality at 3 wk after treatment and fall treatments in 2002 substantially reduced bentgrass quality. Summer treatments were more effective than spring or fall treatments in reducing annual bluegrass cover. Final evaluations revealed 36, 31, 21, and 26% annual bluegrass cover averaged across nontreated, spring-treated, summer-treated, and fall-treated plots, respectively. This study demonstrates that two split applications of bispyribac-sodium at 74 g/ha in summer can effectively reduce annual bluegra...

https://bioone.org/journals/weed-technology/volume-20/issue-3/WT-04-314R2.1/Seasonal-Effects-on-Annual-Bluegrass-Poa-annua-Control-in-Creeping/10.1614/WT-04-314R2.1.pdf

Seasonal Effects on Annual Bluegrass (Poa annua) Control in Creeping Bentgrass with Bispyribac-Sodium'

Summer decline of creeping bentgrass [Agrostis palustris Huds. (=Agrostis stolonifera var. palustris (Huds.) Farw.] root growth is an annual concern in many regions of the USA. A 2-yr field study was conducted to investigate the effects of mowing height and plant growth regulator (PGR) treatments on root biomass (RB) patterns in Penncross' creeping bentgrass, grown on a Wakulla sand (sandy, siliceous, Thermic Psammentic Hapludults) with 94% sand, 4% silt, 2% clay, 24 mg g -1 organic matter, and a pH of 6.1. Plots were maintained at 3.2, 4.0, or 4.8 mm throughout the experiment. Plant growth regulator treatments were trinexapac-ethyl, [4-(cyclopropyl-α-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] applied at 0.05 kg a.i. ha -1 and paclobutrazol, {(±)-(R * ,R * )-β-[(4-chloro-phenyl) methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol} applied at 0.14, 0.28, or 0.56 kg a.i. ha -1 . Plant growth regulator treatments initially were applied in April 1997 and were reapplied monthly for 24 mo. Annual variation in air and soil temperature accounted for variable RB across years. Root biomass declined 76% from a May maximum to a minimum in September; however, RB increased between September and January. Turf mowed to a height of 3.2 mm consistently had lower RB than turf maintained at 4.0 or 4.8 mm, and had slower early autumn RB recovery. When averaged across mowing heights, only paclobutrazol (0.56 kg a.i. ha -1 ) reduced RB and no PGR increased rooting when compared with nontreated turf. From September to January of each year, a PGR by mowing height interaction showed that paclobutrazol applied at 0.56 kg a.i. ha -1 delayed RB recovery in turf mowed to a height of 4.8 mm, while no PGR delayed RB recovery in turf maintained at the 3.2 mm mowing height. Slower RB recovery in turf mowed to 3.2 mm following the September minimum RB was attributed to reductions in turf quality and density, rather than the effects of PGRs. Paclobutrazol only reduced Penncross RB when applied at twice the labeled rate and with greater application frequency than is typical for most PGR use patterns. These results showed that labeled rates of paclobutrazol and trinexapac-ethyl did not adversely affect root growth under putting green conditions.

Plant Growth Regulator and Mowing Height Effects on Seasonal Root Growth of Penncross Creeping Bentgrass

Summary


1. Poa annua (annual meadow-grass or annual bluegrass) is the most problematic weed of temperate zone golf putting greens. In the UK there are no chemicals approved for its control, although several herbicides and plant growth regulators are available in the USA. Reducing P. annua levels in fine turf would greatly reduce the heavy reliance on pesticides and water that currently exists.



2. This paper reports on an observational and a manipulative study in golf putting greens, aimed at determining whether arbuscular mycorrhizal (AM) fungi have any potential for the reduction of this weed in fine turf.



3. All 18 greens on three golf courses were sampled, and in two courses a negative relation between AM fungi and P. annua abundance was found, upholding previous results. In greens where AM fungi were relatively common (as measured by root colonization), P. annua was rare, and vice versa. Furthermore, when the fungi were common, abundance of the desirable turfgrass Agrostis stolonifera was greater.



4. Two explanations are suggested for these relations, a competitive one, in which AM fungi alter the balance of competition between the two grasses, and an antagonistic one, in which the fungi may directly reduce the growth of P. annua.



5. In a manipulative experiment, where mycorrhizal inoculum was added to a golf green, the colonization level of A. stolonifera roots was enhanced, as was the abundance of this grass. Furthermore, there was a suggestion that adding inoculum could decrease the abundance of P. annua.



6. AM fungi have the potential to be a much more environmentally sound method of P. annua control in sports turf than the currently used chemicals.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2664.1999.00456.x

Can arbuscular mycorrhizal fungi be used to control the undesirable grass Poa annua on golf courses

Paclobutrazol and flurprimidol were evaluated for suppression of a perennial subspecies of annual bluegrass in a creeping bentgrass green. Three applications of paclobutrazol in the spring (Mar. 17, Apr. 17, and May 17) followed by three applications in the fall (Oct. 2, Nov. 2, and Nov. 30) suppressed the perennial subspecies ≥ 72% at 3 wk after the final treatment. However, suppression was reduced to ≤ 57% by 4 mo after the final fall application. Flurprimidol applied in three spring and three fall applications did not suppress the perennial subspecies as effectively as paclobutrazol. Suppression was ≤ 47% at 3 wk after the final flurprimidol treatment and was only ≤ 20% by mid-March. Neither chemical injured creeping bentgrass greater than 20% in the spring. However, leaf discoloration injury from the initial October application ranged from 26 to 30% for paclobutrazol in 1993 and 21 to 28% for flurprimidol in 1994. When injury occurred in October it was temporary and the creeping bentgrass recovered within 3 to 4 wk. Paclobutrazol and flurprimidol applied in November did not injure creeping bentgrass. Nomenclature: Flurprimidol, α-( 1 -methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidine-methanol; paclobutrazol, (±)-(R * R * ) β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2- 4-triazole- 1-ethanol; Poa annua spp. reptans (Hausskn.) Timm. # 3 POAAN; creeping bentgrass, Agrostis stolonifera L. 'Penncross.'

Suppression of a Perennial Subspecies of Annual Bluegrass (Poa annua spp. reptans) in a Creeping Bentgrass (Agrostis stolonifera) Green with Plant Growth Regulators

Field experiments were conducted to determine the effects of foliar iron (Fe) applied with postemergence herbicides on injury, color, and quality of 'Tifway' bermudagrass (Cynodon transvaalensis Burtt-Davy × Cynodon dactylon (L.) Pers.). Iron significantly decreased injury and improved quality and color of 'Tifway' bermudagrass in conjunction with herbicide treatment. Turf injury was less for 4 to 18 days after the initial MSMA application when Fe was added. Injury was also less from sequential Fe treatment with MSMA + metribuzin (up to 4 days) and MSMA + imazaquin (from 4 to 10 days) compared to the respective herbicides applied alone. There was no difference in turf injury from Fe when imazaquin at 1.3 kg·ha -1 was applied as a single treatment. However, turf treated with Fe and two applications of imazaquin (9- to 10-day interval) recovered from herbicide injury faster than when treated only with the herbicide. Iron did not prevent immediate 2,4-D + mecoprop + dicamba injury to the bermudagrass, but did hasten turf recovery from injury at 26 days after treatment. With a few exceptions, 'Tifway' bermudagrass quality was higher and color improved when Fe was added. However, injury expressed as loss of shoot density was not affected by Fe and only injury expressed as color loss was improved by Fe. Chemical names used: 3,6-dichloro- 2-methoxybenzoic acid (dicamba), 2-(4,5-dihydro-4-methyl)-4-(1-methylethyl)-5-oxo-1H-imidazol-2yl)-3-quinolinecar- boxylic acid (imazaquin), (± )-2-(4-chloro-2-methylphenoxy)propanoic acid (mecoprop), 4-amino-6-(1,1-dimethyle- thyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one (metribuzin), monosodium salt of MAA (MSMA), and (2,4-dichlor- ophenoxy)acetic acid (2,4-D). Postemergence herbicides are necessary to control emerged weeds in bermudagrass turf. For example, MSMA (Johnson, 1975) has been used for control of large crabgrass (Digitaria sanguinalis L. Scop.), MSMA + metribuzin (Johnson, 1980) for goosegrass (Eleusine indica L. Gaertn.) imazaquin or MSMA + imazaquin (Coats et al., 1987) for purple nutsedge (Cyperus rotundus L.), and 2,4-D + mecoprop + dicamba for various broadleaf weeds (Johnson, 1987). Although these herbicides are labeled for bermudagrass, various degrees of turf injury usually occur within a few days following herbicide application. Injury may be expressed as loss of shoot density and/or discoloration. Slight to moderate discoloration of bermudagrass occurred when treated with MSMA (Johnson, 1981) or imazaquin (Coats et al., 1987), while severe injury was reported when the grass was treated with MSMA + metribuzin (Johnson, 1980) or 2,4-D + mecoprop + dicamba (Johnson, 1978, 1983). However, bermudagrass fully recovered within 2 to 4 weeks after herbicide treatments regardless of the amount of initial injury.

/pdf/foliar-applied-iron-enhances-bermudagrass-tolerance-to-1449tshfeq.pdf

Foliar-applied Iron Enhances Bermudagrass Tolerance to Herbicides

Seashore paspalum is used on golf courses in warm temperate regions, but prolific growth and seedhead development may reduce turfgrass quality. Field experiments were conducted to investigate efficacy of flazasulfuron and trinexapac-ethyl on seashore paspalum seedhead suppression, clipping reduction, and canopy height. Flazasulfuron applied from 4.5 to 27 g ai ha−1 increased clipping reductions from the untreated by 22 to 75% and seedhead suppression from the untreated by 16 to 86% at 2 to 4 wk after treatment. Trinexapac-ethyl applied alone at 96 g ai ha−1 provided erratic levels of seedhead suppression from the untreated, but reduced clippings by approximately 50 to 75% from nontreated by 2 to 4 wk after treatment. On several dates, trinexapac-ethyl enhanced clipping reductions and seedhead suppression from flazasulfuron compared to flazasulfuron alone. Trinexapac-ethyl exacerbated seashore paspalum injury from high flazasulfuron rates (18 to 27 g ha−1) but injury never exceeded 23%. Trinexapac...

https://bioone.org/journals/weed-technology/volume-25/issue-1/WT-D-10-00009.1/Seashore-Paspalum-Seedhead-Control-and-Growth-Regulation-with-Flazasulfuron-and/10.1614/WT-D-10-00009.1.pdf

Seashore Paspalum Seedhead Control and Growth Regulation with Flazasulfuron and Trinexapac-Ethyl

Field studies evaluated the effect of brown patch control on preemergence herbicide efficacy in tall fescue. Pendimethalin (1.7 followed by [fb] 1.7; 3.4 kg ai/ha), prodiamine (0.7 fb 0.6; 1.3 kg ai/ha), and oxadiazon (2.2 fb 2.2; 4.5 kg/ha), applied sequentially and as a single application, were evaluated for smooth crabgrass control with and without the use of azoxystrobin, a fungicide that controls brown patch. Azoxystrobin suppressed brown patch and increased smooth crabgrass control with pendimethalin in both years. This enhanced efficacy with azoxystrobin was attributed to improved tall fescue turf density and thus increased competition between this turf species and smooth crabgrass. Longer soil-residual herbicides such as oxadiazon and prodiamine provided high levels of smooth crabgrass control (often >90%). With the exception of oxadiazon at 4.5 kg ai/ha in 2000, smooth crabgrass control with oxadiazon and prodiamine was unaffected by the use of azoxystrobin. Nomenclature: Azoxystrobin, methyl (E)...

Effect of Brown Patch (Caused by Rhizoctonia solani) Control on Preemergence Herbicide Efficacy in Tall Fescue (Festuca arundinacea)1

Field studies were conducted in 2001 and 2002 to determine the effect of clethodim, sethoxydim, and halosulfuron on centipedegrass seedhead suppression, seed yield, and seed germination. Clethodim (0.28 kg/ha), sethoxydim (0.31 kg/ha), and halosulfuron (0.06 kg/ha) applications were made at −2, 0, 2, 4, and 6 wk after mowing stopped (WAMS) in each year. Seedhead suppression varied in severity between 2001 and 2002, with increased suppression in 2001. Clethodim reduced seedhead emergence 50 and 33% when applied at 2 and 4 WAMS, respectively, in 2001. Sethoxydim reduced seedhead emergence by 21 and 18% when applied at 2 and 4 WAMS, respectively, in 2001. Halosulfuron had no effect on seedhead emergence in either year and did not reduce seed yield at any application timing. Clethodim reduced seed yield between 22 and 44% at all application timings. The pattern of yield reduction from sethoxydim was similar to that caused by clethodim; however, yield reduction with sethoxydim ranged between 7 and 48% for all ...

Tim R. Murphy

Papers

Suppression of a Perennial Subspecies of Annual Bluegrass (Poa annua spp. reptans) in a Creeping Bentgrass (Agrostis stolonifera) Green with Plant Growth Regulators

Foliar-applied Iron Enhances Bermudagrass Tolerance to Herbicides

Seashore Paspalum Seedhead Control and Growth Regulation with Flazasulfuron and Trinexapac-Ethyl

Effect of Brown Patch (Caused by Rhizoctonia solani) Control on Preemergence Herbicide Efficacy in Tall Fescue (Festuca arundinacea)1

Effects of Postemergence Herbicides on Centipedegrass Seed Production1