Bermudagrass Greens Research Articles

Herbicide effects on dormant and postdormant hybrid bermudagrass putting green turf

AbstractHerbicide resistance coupled with a dearth of selective herbicide options has increased the complexity of annual bluegrass control in hybrid bermudagrass putting greens. Cumyluron, endothall, and methiozolin are herbicides that control annual bluegrass by inhibiting novel sites of action compared with the herbicides currently used for turfgrass management in the United States. However, peer-reviewed literature contains no information on hybrid bermudagrass putting green tolerance to these herbicides. Sixteen field studies were established on eight golf greens in Midlothian, VA, in 2021 and 2022 to evaluate effects of cumyluron, endothall, methiozolin, pronamide, and trifloxysulfuron on bermudagrass spring transition. The 16 studies were split equally between initiation during full dormancy versus mid-spring transition. Methiozolin applied at 500 and 1,000 g ai ha−1 typically increased the heat units (growing degree days with a base temperature of 15 C) required for hybrid bermudagrass to visibly achieve 90% green coverage (T90) when applied to fully dormant hybrid bermudagrass. This delay in green coverage was more pronounced at sites where hybrid bermudagrass vigor was seemingly reduced via abiotic stressors. Endothall was generally more injurious than all other treatments when applied to hybrid bermudagrass during mid-transition. Endothall applied at 840 g ai ha−1 injured hybrid bermudagrass for 0 to 9 d over a threshold of 30% (DOT30), depending on location. In two site-years characterized by increased abiotic stress, methiozolin applied at 1,000 g ai ha−1 caused 44 DOT30. Cumyluron never injured hybrid bermudagrass by more than 30% or delayed T90 regardless of application timing. These results indicate that methiozolin should be applied only within labeled rates to actively growing hybrid bermudagrass putting greens, cumyluron can be safely applied at 6,450 g ai ha−1 to dormant or actively growing bermudagrass greens, and endothall applications should be limited to dormant bermudagrass greens unless transient phytotoxicity is acceptable.

Evaluation of Different Aerification Methods for Ultradwarf Hybrid Bermudagrass Putting Greens

Aerification and topdressing are important cultural management practices that help prevent organic matter accumulation and soil compaction in golf greens. However, these practices result in surface disruption and decreased putting quality during recovery. A 2-year study was conducted on a ‘TifEagle’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) putting green to determine the effect of different aerification methods and topdressing materials on soil properties and turfgrass recovery. Plots were aerified four times per year (May to Aug.) using 1/2-inch hollow tines, 1/4-inch hollow needle tines, hollow tines 2X + hollow needle tines 2X, or sand injection, and topdressed with either 90:10 (sand:peat) or green-dyed sand. Visual quality, normalized difference vegetation index, percent green cover, dark green color index (DGCI), surface firmness and volumetric water content were measured before initial aerification and at 7 and 21 days after aerification. Saturated hydraulic conductivity (Ksat) and organic matter (OM) content were measured monthly. Aerification with hollow tines and hollow tines 2X + hollow needle tines 2X resulted in lower firmness and OM and higher Ksat compared with hollow needle tines and sand injection. Sand injection showed the highest percent green cover and similar OM content compared with hollow tines and hollow tines 2X + hollow needle tines 2X. Green-dyed sand showed a higher percent green cover and DGCI compared with 90:10 sand:peat. Using hollow tines only or alternating them with hollow needle tines is the best option to decrease OM content while increasing Ksat in hybrid bermudagrass greens; however, their use could result in slower turfgrass recovery compared with other aerification methods.

Identification, frequency of occurrence, and inoculum density of select ectotrophic root‐infecting fungi within ultradwarf hybrid bermudagrass greens in Mississippi

AbstractGaeumannomyces graminis var. graminis (Sacc.) Arx & Oliver was described as a pathogen of bermudagrass decline [takeall root rot (TARR)]; however, recent studies have reported that multiple ectotrophic root‐infecting (ERI) fungi are associated with root rot in ultradwarf hybrid bermudagrass (UDHB) [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] putting greens. This study surveyed UDHB roots from a healthy and a TARR‐symptomatic green. Real‐time polymerase chain reaction multiplex assays facilitated the rapid identification and quantification of four ERI fungi: G. graminis, G. nanograminis P.L Vines & M. Tom.‐Pet., Magnaporthiopsis cynodontis P.L Vines & M. Tom.‐Pet., and Candidacolonium cynodontis P.L Vines & M. Tom.‐Pet. Gaeumannomyces nanograminis was identified more frequently than G. graminis in roots from the healthy green and had the greatest inoculum density in 2018. In contrast, G. graminis was identified in 80% more root samples than G. nanograminis in the TARR‐symptomatic green in 2017, and the inoculum density of G. graminis was >2 M DNA copies per 2‐µl DNA sample. Magnaporthiopsis cynodontis was the predominant fungus in both greens throughout the study; however, its inoculum density was the lowest among all four ERI fungi. Two or more ERI fungi were frequently identified as co‐colonizing UDHB roots. This study showed that multiple ERI pathogens were widely distributed throughout the roots of two UDHB greens regardless of symptom expression and confirmed that ERI complexes co‐colonize UDHB roots. This is the first study documenting the widespread occurrence and inoculum density levels of multiple ERI fungi colonizing UDHB roots.

Effects of growing degree day based trinexapac‐ethyl application on ultradwarf hybrid bermudagrass putting green quality and ball roll

AbstractApplication of plant growth regulators to hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] putting greens is a common management practice used to reduce clipping yield and improve aesthetic and functional turfgrass quality. Growing degree day (GDD) models have explored the effects of plant growth regulator application timing on ultradwarf hybrid bermudagrass clipping yield. However, there is a need for research evaluating effects of GDD‐timed plant growth regulator applications on turfgrass quality and ball roll. A field study was conducted in summer 2018 at three locations (Knoxville, TN; Raleigh, NC; and Starkville, MS) to determine the effects of trinexapac‐ethyl (TE) applied according to a GDD model on ultradwarf hybrid bermudagrass putting green quality and ball roll compared to calendar‐based treatment (i.e., weekly or twice‐weekly). For GDD applications, TE was applied at either 20 or 33 g ha−1. GDD based applications were made once 220 GDD (base 10°C) accumulated after each treatment. TE was applied at either 20 or 33 g ha−1 for weekly treatments and rate reduced to either 14 or 16 g ha−1 for the twice‐weekly treatment. In all locations, TE applied on a 220 GDD10C schedule resulted in turfgrass quality greater than or equal to that of the weekly and twice‐weekly applied treatments. Ball roll distance was slightly lower in plots treated with TE every 220 GDD10C compared to the weekly and twice‐weekly treatments, although differences may be negligible to golfers (13 to 23 cm). Ball roll distance was negatively correlated with clipping yield (−0.37 to −0.69). Turfgrass managers choosing to regulate ultradwarf hybrid bermudagrass greens with TE should consider applying on a GDD rather than calendar‐based interval to achieve improved turfgrass quality without sacrificing ball roll distance.

Viscosity Is Linked to Temporal Behavior of Hydrocarbon Injury on a Bermudagrass Green

Core Ideas Temporal behavior of hydrocarbon injury varied with hydrocarbon fluid type. Descriptors of injury behavior correlated with kinematic viscosity of hydrocarbon fluids. Injury from high‐viscosity fluids began healing later and had longer recovery times.

Kinetics of Hydrocarbon Induced Visual Green Color Loss on a Bermudagrass Green

Core Ideas Kinetics models are essential to understanding complex dynamic processes.The kinetics of visual green color loss in turfgrass shoots is poorly understood.Kinetics of visual green color loss in turfgrass shoots in response to treatment with hydrocarbons was investigated.Rate and reaction order of visual green color loss in response to treatment with hydrocarbons were determined.Determining rate of and reaction order for visual green color loss increased understanding of color loss dynamics. Hydrocarbon machine fluids (MF) injure turf, inducing visual green color loss (VGCL) with onset of shoot necrosis. The dynamics of MF‐induced VGCL are unknown, having never been described. This research was conducted to increase understanding of color loss dynamics by investigating the kinetics of MF‐induced VGCL on a hybrid bermudagrass green (Cynodon dactylon [L.] Pers. var. dactylon × C. transvaalensis Burtt‐Davy). The effect six different MF had on changes in hue angle (θ) of shoots with time (t) was explained using digital image analysis (DIA) and curve fitting. Treating shoots with MF decreased mean θ from 88° at day zero to 33° at 12 d, as shoot color changed from green to brown. Fitting an exponential decay model of the form θ = θ0 + a0e‐kt to dθ/dt data revealed the rate of VGCL (−k) ranged from −4.45 d−1 (motor oil) to −0.16 d−1 (vegetable hydraulic oil) varying with MF (p < 0.01). Curve fitting also revealed dθ/dt was a first order reaction; plots of ln(θ − θ0) vs. t were linear (R2 = 1.0) for all six MF, while plots of zero order, half order, and second order reactions were not. Determining the rate of MF‐induced VGCL and its reaction order increased understanding of color loss dynamics by giving mathematical meaning to the processes. This was a step forward in understanding turfgrass injury behavior. The approach used for examining VGCL dynamics was inexpensive and nondestructive, and may be useful for other researchers studying plant color dynamics.

Nonlinear Regression Modeling of Hydraulic Oil Injury on a Bermudagrass Green

Hydraulic oil (HO) injures putting greens. Fitting a nonlinear regression model to injury area (IA) with time may help assess injury response to treatment. Modeling was used to determine if washing spills of three HOs with water changes injury dynamics. Effects of HO type and washing on rate of change of IA, time to maximum IA expansion (ME), and IA contraction (healing) times were studied in 2014 at North Fort Myers, FL, on a hybrid bermudagrass green [Cynodon dactylon (L.) Pers. var. dactylon × C. transvaalensis Burt‐Davy ‘TifEagle’ (PP11163)]. Washing changed injury dynamics for synthetic HO (SHO) but had less effect on vegetable HO (VHO) and petroleum HO (PHO). Washing spills of SHO slowed the initial rate of injury expansion from 7.0 to 5.4 sqrt‐cm2 + 0.1 sqrt‐d−1 (p = 0.0969) and increased the rate of injury contraction from −0.36 to −0.83 sqrt‐cm2 + 0.1 sqrt‐d−1 (p < 0.0001). In unwashed SHO plots, IA decreased from a maximum of 21.7 cm2 at 4.5 d to 12.6 cm2 at 38 d (Δ IA = −42%). In washed SHO plots, IA decreased from 18.5 cm2 at 3.8 d to 2.2 cm2 at 38 d (Δ IA = −88%). Calculated healing time for SHO injury was 224 d (unwashed) vs. 65 d (washed). For VHO and PHO, healing took >400 d washed or not. Curve fitting was a novel approach to assessing HO injury response to treatment and illustrated injury behavior that was previously unknown.

Seasonal Cultural Management Practices for Aging Ultradwarf Bermudagrass Greens in the Subtropics: I. Nitrogen and Potassium Fertilization

Bermudagrass cultivars [Cynodon transvaalensis (L.) Pers. × Cynodon dactylon (Burtt‐Davy)] with more decumbent growth habits referred to as “ultradwarfs” have been released for use on golf course greens and tees as an alternative to standard bermudagrass varieties that have been used for >40 yr. Little research information is available on long‐term ultradwarf management requirements in subtropical environments. Therefore, a 4‐yr experiment was conducted in South Florida on a United States Golf Association specified green to determine the effects of nitrogen (N) fertility and N to potassium (K) ratios on quality, growth, and performance of three commercially released ultradwarfs (‘Champion’, ‘TifEagle’, and ‘FloraDwarf’). For all three cultivars, fertilizing at 879 kg N ha−1 yr−1 resulted in acceptable turfgrass quality with mean tissue N and K concentrations of 31 g N kg−1 and 14 g K kg−1, respectively. Over the 4‐yr experiment, leaf tissue N and K were present approximately as a 2:1 ratio, regardless of N rate and N:K ratio applied. As the ultradwarfs aged, fertilizing with 586 kg N ha−1 yr−1 was adequate. It appears that Champion and TifEagle have different mechanisms for increasing aboveground growth and had better quality and growth characteristics than FloraDwarf. This research documented the need for adjusting fertilization as the ultradwarf bermudagrass green ages and for the ultradwarf cultivar maintained.

Documenting Changes in USGA Specification Rootzone Properties in Ultradwarf Bermudagrass Greens

The United States Golf Association (USGA) Green Section has specifications for putting green construction to provide uniform playability and performance throughout the golfing season. However, it is recognized that chemical and physical rootzone properties of these greens change over time. To monitor and characterize these changes, thatch, organic matter (OM) accumulation, and saturated hydraulic conductivity (Ksat) of two ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] greens on four southern Florida golf courses (i.e., eight greens total) were measured over an 8‐yr period from 2006 through 2013. Over time, thatch thickness stabilized at 2.5 cm or less, whereas the OM stained layer increased in thickness to nearly 10 cm. The OM content fluctuated during the year in response to summer cultivation programs (i.e., verticutting and hollow‐core aerification), but OM content was typically greater in spring than in fall. The Ksat was typically lower in spring and higher in fall, which could be attributed to summer cultivation practices and OM content. Golf course superintendents who routinely monitor thatch, OM, and Ksat on their ultradrawf bermudagrass USGA‐specification sand‐based greens can potentially use that information to illustrate to their stakeholders why summer cultivations are necessary, and what has been achieved from a summer cultivation program.

Seasonal Cultural Management Practices for Aging Subtropic Ultradwarf Bermudagrass Greens: II. Mechanical Practices of Topdressing and Verticut Frequency

To provide optimum playing surfaces, many golf courses have used ultradwarf bermudagrass [Cynodon transvaalensis Burtt Davy × C. dactylon (L.) Pers.] cultivars for greens, although little is known about regionally defined cultural management. A 4‐yr experiment was conducted in southern Florida, on a US Golf Association (USGA)‐specified green to examine the effect of topdressing and vertical mowing frequency on ultradwarf bermudgrass cultivars Champion, TifEagle, and FloraDwarf for primarily quality, growth, tissue N and K, and ball roll distance. Weekly topdressing during the wet season enhanced quality and reduced the presence of disease‐like symptoms. TifEagle increased aboveground growth when topdressed weekly compared with Champion and FloraDwarf. As the green aged, however, topdressing biweekly during dry‐season months became important for maintaining quality. Influence of vertical mowing on all observations and measurements were minimal and not consistent from season to season. Further long‐term research is needed to determine how changing mechanical management on a seasonal basis can optimize ultradwarf bermudgrass for quality, vigor, and performance.

Response of ‘TifEagle’ Bermudagrass (Cynodon dactylon × Cynodon transvaalensis) to Ethephon and Trinexapac-ethyl

Turf managers combine ethephon with trinexapac-ethyl (TE) on bentgrass greens to suppress annual bluegrass, inhibit turf growth, and enhance turf quality; however, effects of this growth regulator combination have not been reported on bermudagrass greens. Two experiments were conducted at the Clemson University Greenhouse Complex to investigate the response of ‘TifEagle’ bermudagrass to ethephon and TE. TifEagle bermudagrass plugs were placed in pots with 23-cm depths, 324-cm2 total surface areas, and a soil medium of an 85:15 (v/v) sand and peat moss mix. Ethephon was applied at 0, 3.8 (EP1), and 7.6 (EP2) kg ai/ha/3 wk with TE at 0 and 0.04 kg ai/ha/ 3 wk over a 9-wk period. Initial responses of bermudagrass to ethephon included chlorotic leaves and severe thinning. Bermudagrass treated with ethephon had quality reduced as much as 33% from nontreated turf. TE enhanced turf quality 4 to 22% from 4 to 9 wk after initial treatment. TE helped mask ethephon-induced quality decline after the third application. In the presence of TE, bermudagrass clipping yield was reduced from nontreated turf by 57, 70, and 72% when ethephon was applied at 0, 3.8, and 7.6 kg/ha/3 wk. Ethephon linearly reduced root mass after 9 wk from nontreated turf by 20 and 33% at 3.8 and 7.6 kg/ha/3 wk, respectively. Compared with respective ethephon rates alone, bermudagrass treated with TE and ethephon at 0, 3.8, and 7.6 kg/ha/3 wk, averaged 28, 8, and 15% more root mass. Ethephon at 3.8 and 7.6 kg/ha/3 wk without TE reduced TifEagle bermudagrass root length 14 and 16%, respectively, compared with untreated turf. Bermudagrass treated with ethephon at 0, 3.8, and 7.6 kg/ha/3 wk with TE averaged 3, 11, and 17% higher root length compared with respective ethephon rates after 9 wk. Overall, ethephon may have negative effects on TifEagle root mass, root length, and turf quality. However, combining ethephon with TE may help reduce these deleterious effects.

Influence of Fall-applied Treatments on Spring Transition of an Overseeded Bermudagrass Green

Bermudagrass [Cynodon dactylon (L.) Pers × C. transvaalensis Burtt-Davy] greens across the southern United States are normally overseeded in the fall to provide a uniform green playing surface and tolerance to wear during winter bermudagrass dormancy. The spring transition from overseed grass back to bermudagrass is a major problem associated with overseeding because there can be a decline in putting green quality and playability. There have been recommendations, but relatively few published reports, on the effect of treatments associated with seedbed preparation and overseeding on bermudagrass spring transition. The objective of this 2-year study was to determine if spring transition of an overseeded `Tifgreen' bermudagrass green was influenced by fall-applied scalping level, chemical, and seed rate treatments. Treatment factors and levels were designed to reflect the range of practices used by golf course superintendents in the region at the time of the study. The green was located in the Palm Springs, Calif. area, which has relatively mild winters and a low desert, southern Calif. climate. The first year of the study was from September 1996 to July 1997 and the second year was from September1997 to July 1998. Scalping level treatments included a moderate and severe verticut and scalp; chemical treatments included a check, trinexapac-ethyl at two rates, and diquat; and seed rate treatments included a high and low rate of a mixture of `Seville' perennial ryegrass (Lolium perenne L.) and `Sabre' rough bluegrass (Poa trivialis L.). The plot was maintained under golf course conditions and a traffic simulator was used to simulate golfer traffic. Visual ratings of percent green bermudagrass coverage were taken every 3 weeks from 20 Feb. 1997 to 29 July 1997 and from 11 Nov. 1997 to 22 July 1998. Visual turfgrass quality ratings were taken during the second year of the study. Results showed that spring transition was not influenced by fall-applied treatments during both years. Also, visual turfgrass quality was not influenced during the second year. Chemical names used [4(cyclopropyl-_hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl); 9,10-dihydro-8a-, 10a-diazoniaphenanthrene (diquat).

Influence of Fall-applied Treatments on Spring Transition of an Overseeded Bermudagrass Green

Bermudagrass [Cynodon dactylon (L.) Pers × C. transvaalensis Burtt-Davy] greens across the southern United States are normally overseeded in the fall to provide a uniform green playing surface and tolerance to wear during winter bermudagrass dormancy. The spring transition from overseed grass back to bermudagrass is a major problem associated with overseeding because there can be a decline in putting green quality and playability. There have been recommendations, but relatively few published reports, on the effect of treatments associated with seedbed preparation and overseeding on bermudagrass spring transition. The objective of this 2-year study was to determine if spring transition of an overseeded `Tifgreen' bermudagrass green was influenced by fall-applied scalping level, chemical, and seed rate treatments. Treatment factors and levels were designed to reflect the range of practices used by golf course superintendents in the region at the time of the study. The green was located in the Palm Springs, Calif., area, which has relatively mild winters and a low desert, southern California climate. The first year of the study was from Sept. 1996 to July 1997 and the second year was from Sept. 1997 to July 1998. Scalping level treatments included a moderate and severe verticut and scalp; chemical treatments included a check, trinexapac-ethyl at two rates, and diquat; and seed rate treatments included a high and low rate of a mixture of `Seville' perennial ryegrass (Lolium perenne L.) and `Sabre' rough bluegrass (Poa trivialis L.). The plot was maintained under golf course conditions and a traffic simulator was used to simulate golfer traffic. Visual ratings of percent green bermudagrass coverage were taken every 3 weeks from 20 Feb. 1997 to 29 July 1997 and from 11 Nov. 1997 to 22 July 1998. Visual turfgrass quality ratings were taken during the second year of the study. Results showed that spring transition was not influenced by fall-applied treatments during both years. Also, visual turfgrass quality was not influenced during the second year. Chemical names used: [4(cyclopropyl-αhydroxy-methylene) -3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl); 9,10-dihydro-8a-, 10a-diazoniaphenanthrene (diquat).

Fenarimol Tolerance of Roughstalk Bluegrass Overseeded in Bermudagrass Greens

AbstractBermudagrass (Cynodon spp.) putting greens are overseeded with cool‐season grasses in the fall to maintain a high‐quality putting turf throughout the southern USA. Perennial ryegrass (Lolium perenne L.) has been the predominant grass used for overseeding until recently, when roughstalk (Poa trivialis L.) has been increasingly used for overseeding. Annual bluegrass (Poa annua L.) is a problem winter annual weed that infests most overseeded bermudagrass greens and the weed must be controlled with a herbicide to maintain a high‐quality putting surface. Fenarimol [ɑ(2‐chlorophenyl)‐ɑ‐(4‐chlorophenyl)‐5‐pyrimidinemethanol] has preemergence herbicidal activity on annual bluegrass, but it may also reduce the germination and establishment of roughstalk bluegrass seedlings. A field experiment was conducted over a 2‐yr period to determine the time interval of fenarimol treatments necessary to avoid injury to roughstalk bluegrass overseeded on a bermudagrass green. Overseeded roughstalk bluegrass tolerated fenarimol when applied as (i) a single application at 2.7 kg ha−1, (ii) two applications of 2.0 kg ha−1 each, and (iii) three applications of 1.4 kg ha−1 each, provided the final application was made ≥ 2 wk before overseeding. Quality and density of roughstalk bluegrass were not influenced by fenarimol, provided the last application was made ≥ 2 wk before overseeding in 1991 and ≥ 1 wk before overseeding in 1992. When the final fenarimol application was made during this period, the transition of overseeded roughstalk bluegrass back to bermudagrass was not affected the following spring and early summer.

Influence of Herbicides on Bermudagrass Greens Overseeded With Perennial Ryegrass

Abstract Two field experiments were initiated to determine the effects of herbicides on turfgrass quality and spring to summer transition from overseeded perennial ryegrass (Lolium perenne L.) back to ‘Tifway’ bermudagrass [Cynodon transvaalensis Burtt-Davy × Cynodon dactylon (L.) Pers.]. Pendimethalin applied at 3.3 kg·ha−1 in early March hastened the transition from ryegrass to bermudagrass in one of two years, but 1.7 kg·ha−1 applied in each of two applications did not. A single application of pronamide at 0.28 kg·ha−1 hastened the transition of overseeded ryegrass to bermudagrass without severely injuring either turfgrass. Oryzalin, oryzalin + benefin, or paraquat severely reduced the quality of ryegrass, while oxadiazon at 3.3 kg·ha−1, oxadiazon + benefin, glyphosate, metribuzin, or MSMA did not affect transition from overseeded ryegrass to bermudagrass when compared with nontreated turfgrass. This study illustrates the potential for some herbicides to enhance the transition from perennial ryegrass to bermudagrass. Chemical names used: N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine (benefin); dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate (DCPA); (±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); N-(phosphonomethyl)glycine (glyphosate); N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyI]acetamide (mefluidide); 4-amino-6-(1,1-dimethylethyl)-3-(methylthiol)-1,2,4-triazin-5(4H)-one (metribuzin); monosodium salt of MAA (MSMA); 4-(dipropylamino)-3,5-dinitrobenzene-sulfonamide (oryzalin); 3-[2,4-dichloro-5-(1-methylethoxy)-phenyl)-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one-(oxadiazon); 1,1'-dimethyl-4,4'-bipyridinium salts (paraquat); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzamine (pendimethalin); and 3,5-dichloro(N-1,1-dimethyl-2-propynyl)benamide (pronamide).

Influence of Aeration, Topdressing, and Vertical Mowing on Overseeded Bermudagrass Putting Green Turf

Abstract Field studies were conducted for 4 years on putting green turf to determine the influence of cultivation practices on the transition from overseeded perennial ryegrass (Lolium perenne L. ‘Yorktown II’) turf to hybrid burmudagrass [Cynodon dactylon (L.)Pers. × C. transvaalensis Burtt-Davies] in the spring. The cultivation practices of core aeration, vertical mowing, and topdressing were shown to have no positive influence of increasing the rate of bermudagrass coverage during the spring on bermudagrass greens overseeded with perennial ryegrass. The verticut treatment resulted in decreased bermudagrass coverage as well as a reduction in turf quality. All cultivation practices resulted in some quality loss at various times during the spring transition period compared to the control.

Residual Activity of Herbicide Treatments on Bermudagrass Greens Overseeded with Ryegrass1

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] control is a major problem weed in bermudagrass [Cynodon dactylon (L.) Pers.] putting greens and it is usually necessary to apply postemergence herbicide treatments throughout summer and early fall for effective control. Since bermudagrass greens are overseeded with cool‐season grasses in early fall, a study was conducted on a Cecil (Typic Hapludult) sandy loam at Experiment, Ga. to determine the interval needed between Herbicide treatments and time of overseeding without injuring the newly planted turf.A ‘Tifway’ bermudagrass putting green was treated with MSMA (monosodium methanearsonate), methazole [2‐(3,4‐dichlorophenyl)‐4‐methyl‐l,2,4‐oxadiazolidine‐3,5‐dione], metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐ 5(4H)‐one] and combinations of MSMA with either methazole or methribuzin at 0, 1, 2, 4, and 6 weeks before overseeding with perennial ryegrass (Lolium perenne L. ‘Medalist IV’ and ‘Medalist V’). Methazole applied alone was the only herbicide that required at least 1 week between treatment and overseeding without affecting the stand of newly planted turf. Metribuzin applied on day of overseeding significantly reduced seedling vigor but not turf stand. Combinations of MSMA with either methazole or metribuzin did not affect growth of ryegrass when applied anytime up to the day of overseeding.

Phytotoxicity of Herbicides to a Tifgreen Bermudagrass Green

A ‘tifgreen’ bermudagrass [Cynodon dactylon(L.) Pers.] golf-type green was treated with seven preemergence and one postemergence type herbicides at two rates each for three consecutive years to assess their phytotoxicity. A few herbicides were applied on a second, third, and fourth treatment date during the year with applications made in separate plots. Severe foliage injury occurred the first year with siduron [1-(2-methylcyclohexyl)-3-phenylurea] while moderate injury occurred with bromacil (5-bromo-3-sec-butyl-6-methyluracil) and DCPA (dimethyl tetrachloroterephthalate); and slight injury occurred with benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), bensulide [0,0-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl)benzenesulfonamide], and terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate). No injury was observed with bandane (polychlorodicyclopentadiene isomers) and tri-calcium arsenate. Injury to the bermudagrass in the second year following renewal treatments was severe with siduron and bromacil; moderate with benefin, bandane, DCPA, and terbutol; and slight with bensulide and tri-calcium arsenate. Injury in the third year following repeat applications was severe with siduron, terbutol, bandane, bromacil, benefin, and DCPA; slight to moderate with bensulide, and slight with tri-calcium arsenate. Injury observed the fourth year resulting from residues was moderate with bandane; slight with terbutol, benefin, bensulide, and DCPA; and none with siduron, bromacil, and tri-calcium arsenate.

Compressibility of Turf as a Measure of Grass Growth and Thatch Development on Bermudagrass Greens1

AbstractThe object of this study was to develop a method for measuring the variation in compressibility of thatch on bermudagrass experimental and golf course greens and to evaluate the data as an indicator of grass growth and thatch development. A “thatchmeter” was designed to rapidly determine differences in compression between a bearing pressure of 7.3 g/cm2 and one of 570 g/cm2, the former less than that of a golf ball, and the latter, estimated from the weight of an average man. Regressions of compressibility on rate of grass growth and on thatch weight and depth were statistically significant (.001). Compressibility averaged between 6.1 and 11.5 mm per green for 24 golf greens under daily play. A 10‐reading average per plot or green can be obtained in 5 min and requires little professional supervision. The value of the procedure as a research tool is apparent, but specific ranges for acceptable playing quality of golf greens, between excessive hardness and excessive thatch, must be established individually for various grass varieties and environments.