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Published online 1 September 2007
Published in Crop Sci 47:2138-2144 (2007)
© 2007 Crop Science Society of America
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TURFGRASS SCIENCE

Trinexapac-Ethyl Application Regimens Influence Growth, Quality, and Performance of Bermuda Grass and Creeping Bentgrass Putting Greens

Patrick E. McCullougha, Haibo Liub,*, Lambert B. McCartyb and Joe E. Tolerc

a Dep. of Plant Biology and Pathology, Rutgers, The State Univ. of New Jersey, New Brunswick, NJ 08901-8520
b Dep. of Horticulture, Clemson Univ., Clemson, SC 29634-0319
c Dep. of Applied Economics and Statistics, Clemson Univ., Clemson, SC 29634-0319

* Corresponding author (haibol{at}clemson.edu).


   ABSTRACT
TOP
 NOTES
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Dwarf bermudagrass (Cynodon dactylon x C. transvaalensis Burtt-Davy) and creeping bentgrass (Agrostis stolonifera L.) are planted for golf greens in the U.S. transition zone, but management regimes, such as the use of a plant growth regulator (PGR), often vary for long-term culture of the two species. The objective of this experiment was to investigate application regimens of the PGR trinexapac-ethyl (TE), on growth, quality, and performance of creeping bentgrass and bermudagrass putting greens in Clemson, SC. ‘L-93’ creeping bentgrass and ‘TifEagle’ bermudagrass putting greens, established in summer 2002 and mowed at 3.2 mm, received TE over 12 wk in three regimens: 0.017 kg ha–1 wk–1, 0.033 kg ha–1 2 wk–1 (biweekly), or 0.05 kg ha–1 3 wk–1 (triweekly) from May to August 2003 and 2004. Creeping bentgrass was not discolored from TE, but unacceptable bermudagrass discoloration (>20%) occurred on one, two, and six dates for weekly, biweekly, and triweekly regimens, respectively. All TE regimens reduced bermudagrass clippings approximately 50% from nontreated bermudagrass across all dates, while creeping bentgrass clipping reductions, approximately 20 to 35% from nontreated grass, were inconsistent. The root masses of both species treated with TE regimens were similar to nontreated turf. Bermudagrass aerification recovery was reduced on two, two, and four dates after weekly, biweekly, and triweekly TE regimens, respectively. All TE regimens increased morning and evening bermudagrass golf ball roll distance approximately 25 cm from morning distances of nontreated turf.

Abbreviations: PGR, plant growth regulator • TE, trinexapac-ethyl • USGA, United States Golf Association • WAA, week after aerification • WAIT, week after initial treatment

Trinexapac-Ethyl Application Regimens Influence Growth, Quality, and Performance of Bermuda Grass and Creeping Bentgrass Putting Greens

Patrick E. McCullougha, Haibo Liub,*, Lambert B. McCartyb and Joe E. Tolerc

a Dep. of Plant Biology and Pathology, Rutgers, The State Univ. of New Jersey, New Brunswick, NJ 08901-8520
b Dep. of Horticulture, Clemson Univ., Clemson, SC 29634-0319
c Dep. of Applied Economics and Statistics, Clemson Univ., Clemson, SC 29634-0319

* Corresponding author (haibol{at}clemson.edu).

Dwarf bermudagrass (Cynodon dactylon x C. transvaalensis Burtt-Davy) and creeping bentgrass (Agrostis stolonifera L.) are planted for golf greens in the U.S. transition zone, but management regimes, such as the use of a plant growth regulator (PGR), often vary for long-term culture of the two species. The objective of this experiment was to investigate application regimens of the PGR trinexapac-ethyl (TE), on growth, quality, and performance of creeping bentgrass and bermudagrass putting greens in Clemson, SC. ‘L-93’ creeping bentgrass and ‘TifEagle’ bermudagrass putting greens, established in summer 2002 and mowed at 3.2 mm, received TE over 12 wk in three regimens: 0.017 kg ha–1 wk–1, 0.033 kg ha–1 2 wk–1 (biweekly), or 0.05 kg ha–1 3 wk–1 (triweekly) from May to August 2003 and 2004. Creeping bentgrass was not discolored from TE, but unacceptable bermudagrass discoloration (>20%) occurred on one, two, and six dates for weekly, biweekly, and triweekly regimens, respectively. All TE regimens reduced bermudagrass clippings approximately 50% from nontreated bermudagrass across all dates, while creeping bentgrass clipping reductions, approximately 20 to 35% from nontreated grass, were inconsistent. The root masses of both species treated with TE regimens were similar to nontreated turf. Bermudagrass aerification recovery was reduced on two, two, and four dates after weekly, biweekly, and triweekly TE regimens, respectively. All TE regimens increased morning and evening bermudagrass golf ball roll distance approximately 25 cm from morning distances of nontreated turf.

Abbreviations: PGR, plant growth regulator • TE, trinexapac-ethyl • USGA, United States Golf Association • WAA, week after aerification • WAIT, week after initial treatment


   INTRODUCTION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
GOLF COURSES IN THE U.S. transition zone have traditionally planted creeping bentgrass (Agrostis stolonifera L.) for putting green turf, but improved bermudagrass (Cynodon dactylon x C. transvaalensis Burtt-Davy) cultivars are replacing this species because less water, fungicides, and intensive management are required for successful long-term culture (Hanna and Elsner, 1999; McCarty, 2005a). Dwarf-type bermudagrass cultivars, such as ‘TifEagle’, are improved selections with fine leaf textures and low growth habits that tolerate long-term mowing heights of 3.2 mm (White, 1998; Hanna and Elsner, 1999; White et al., 2004). Genetic and morphological variations of dwarf-type cultivars from ‘Tifdwarf’, ‘Tifgreen’, and ‘Tifway’ bermudagrasses produce putting-green quality once exclusive to creeping bentgrass for transition-zone golf courses (Burton, 1991; Hanna and Elsner, 1999; Capo-chichi et al., 2005).

Maintaining consistently uniform playing surfaces is an economically critical aspect of creeping bentgrass and bermudagrass golf green culture that requires intensive management (O'Brien, 1981; Foy, 1991; White, 1998; White et al., 2004; Hollingsworth et al., 2005). However, turf managers often compromise fundamental cultural practices to achieve desired putting green quality and ball roll distances. Practices that promote surface uniformity include lowering mowing heights, double cutting, and periodic rolling, which often reduce turfgrass aesthetics (Hartwiger et al., 2001; McCarty, 2005b). More important, maintaining putting green turf under conditions beyond their physiological capacities may deleteriously affect root growth, turf vigor, and recuperative capabilities from disease, traffic, heat, and other stresses (Beard, 1973; Hartwiger et al., 2001; Fagerness and Yelverton, 2001; Liu and Huang, 2002). Incorporating a plant growth regulator (PGR), trinexapac-ethyl (TE), into putting green maintenance is an alternative to these mechanical methods that may improve surface uniformity without negatively affecting plant health or aesthetics (Fagerness et al., 2000; Fagerness and Yelverton, 2001). Trinexapac-ethyl reduces leaf growth by inhibiting late gibberellin biosynthesis, thus often improving turfgrass quality and performance (Johnson, 1997; Rademacher, 2000; Ervin and Koski, 2001; Heckman et al., 2001a; Tan and Qian, 2003).

Reducing turfgrass shoot growth with TE effectively reduces mowing requirements, improves sod strength, and enhances turfgrass tolerance to shade, disease, and drought stress (Golembiewski and Dannerberger, 1998; Jiang and Fry, 1998; Qian and Engelke, 1999; Fagerness and Yelverton, 2000; Heckman et al., 2001b; Goss et al., 2002; Steinke and Stier, 2003; McCarty et al., 2004; Bunnell et al., 2005). Golf course superintendents also incorporate TE into golf green maintenance regimes to reduce ball roll friction caused by uneven shoot growth. In field experiments, ‘Penncross’ creeping bentgrass treated with periodic TE applications showed temporary ball roll distance enhancements, but long-term improvements were more consistent when mowing height was reduced from 4.8 to 3.2 mm (Fagerness et al., 2000). In summer experiments where TE was applied at 0.04 kg ha–1 4 wk–1, ‘L-93’ creeping bentgrass ball roll distance was enhanced 1 to 2 wk after application, but reduced efficacy before sequential treatments prevented consistency of these effects (McCullough et al., 2006b).

Compared with creeping bentgrass, there has been limited long-term investigation of TE performance on dwarf-type bermudagrass. In a 2-yr experiment investigating nitrogen and TE use on TifEagle bermudagrass, TE applications at 0.05 kg ha–1 3 wk–1 enhanced ball roll distances 15% over nontreated turf, whereas ball roll distances were reduced with increased N rate and from morning to evening (McCullough et al., 2006a). Although TE did not mask diurnal differences in ball roll, bermudagrass treated with TE averaged 10% longer evening distances than morning distances of nontreated turf. In these experiments, spring applications of TE at 0.05 kg ha–1 caused significant discoloration but, TifEagle bermudagrass had better tolerance to sequential summer TE applications (McCullough et al., 2006c). These experiments suggest that TE has beneficial effects for bermudagrass golf green culture, but application regimens should be modified relative to creeping bentgrass greens.

Research is warranted to compare TE efficacy on dwarf bermudagrass with creeping bentgrass when grown as golf greens in the U.S. transition zone. Applying lower TE rates in weekly and biweekly regimens could provide more consistent creeping bentgrass growth inhibition than higher rates at longer (>2 wk) intervals. Furthermore, incremental TE applications at frequent intervals could reduce bermudagrass putting green discoloration without reducing total TE rate applied over the growing season. To test these hypotheses, we investigated the effects of TE application regimens on quality, growth, and performance of L-93 creeping bentgrass and TifEagle bermudagrass putting greens in a 2-yr field experiment.


   MATERIALS AND METHODS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Field experiments were conducted over 12 wk at the Turfgrass Service Center, Clemson, SC, from May to July of 2003 and 2004 on TifEagle bermudagrass and L-93 creeping bentgrass putting greens established in July and August 2002, respectively. Greens were constructed according to United States Golf Association (USGA) specifications (USGA Green Section Staff, 1993). Greens were mowed at 7:00 a.m. 6 d wk–1 at 3.2 mm beginning the first week in April for creeping bentgrass and in May for bermudagrass. Both greens received hand watering and overhead irrigation as needed to prevent plant stress. Creeping bentgrass was aerified 23 Sept. 2003 and 8 Mar. 2004 with 1.3-cm diameter hollow tines with 5 cm spacing. Cores were removed and holes were filled to the surface with similar textured sand to that used for green construction. Beginning the first week of March in both years, creeping bentgrass was fertilized at 6 kg N ha–1 wk–1, with an 18–3–18 (N–P–K) greens-grade granular fertilizer (Anderson's, Maumee, OH). During active spring, summer, and fall growth, creeping bentgrass received preventative fungicide applications including chlorothalonil, azoxystrobin, fosetyl-al, and propiconazole to control dollar spot (Sclerotinia homoeocarpa F.T. Bennet), pythium (Pythium spp.), and brown patch (Rhizoctonia solani Kuhn).

Bermudagrass was aerified with 1.3-cm diameter hollow tines with 5 cm spacing and 10 cm lengths on 20 May and 28 July 2003 and 27 May and 28 July 2004. Cores were removed, and holes were filled as previously stated. Bermudagrass was initially fertilized in late April with 12 kg N ha–1 of ammonium nitrate plus 12 kg N ha–1 of an 18–3–18 (N–P–K) greens-grade granular fertilizer. In May bermudagrass was fertilized at 12 kg N ha–1 wk–1 with the 18–3–18 granular fertilizer until mid-August of both years.

Treatments and Experimental Design
Trinexapac-ethyl, in emulsifiable concentration (1EC), was applied at 0, 0.017 kg ha–1 wk–1, 0.033 kg ha–1 2 wk–1, or 0.05 kg ha–1 3 wk–1 with a CO2 sprayer calibrated at 700 L ha–1 beginning 1 May 2003 and 4 May 2004. Treatment application dates are presented in Table 1 . Experimental design was a randomized complete block with three replications of 1.5- x 2.1-m plots.


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  		Table 1. Trinexapac-ethyl application dates on ‘L-93’ creeping bentgrass and ‘TifEagle’ bermudagrass putting greens, 2003 and 2004, Clemson, SC.

 
Measurements
Discoloration from TE applications was visually rated on a percent scale where 0 = no discoloration and 100% = completely brown turf. Discoloration above 20% was considered unacceptable. Seed-head coverage was visually rated 7 June 2003 and 17 June 2004 on a percent scale, where 0 = no seed heads present and 100 = complete plot coverage. Aerification recovery was visually rated on a percent scale, where 0 = no recovery and 100 = complete turf coverage over aerified areas. Aerification recovery was rated for bermudagrass only since creeping bentgrass was not aerified during the test period.

Clippings were harvested weekly before scheduled TE applications on both the creeping bentgrass and bermudagrass greens, oven-dried at 80°C for 72 h, and then weighed. Two root samples measuring 600 cm3 (30 cm x 20 cm2) were taken per plot on 1 June, 29 June, and 26 July in 2003 and 31 May, 28 June, and 27 July in 2004. Root sa mple holes were backfilled with a similar sand medium on both greens. Roots were washed free of soil and organic matter over sieve screens that prevented loss of root fragments, oven-dried at 80°C for 72 h, and then weighed. Dry weight from the two samples was pooled for each plot before data analysis.

Weekly ball roll distances were measured on the bermudagrass green beginning 1 wk after initial treatment (WAIT). Sampling dates in 2003 were 8, 16, 24, 31 May; 6, 13, 21, 26 June; and 5, 11, 18, 25 July. In 2004, sampling dates were 12, 19, 26 May; 3, 11, 16, 23, 28 June; and 6, 13, 19, 26 July. Six ball roll measurements (three rolls in opposite directions) were made per plot with a 38-cm Stimpmeter (Gaussoin et al., 1995) in the morning from 9:00 to 11:00 a.m. and in the evening at >5:00 p.m. Morning ball roll measurements were made about 2 h after mowing. The Stimpmeter was raised until the golf ball rolled off the cleft located on the opposite end. Ball roll distances were obtained with tape measures laid parallel with plots, and the six rolls were pooled for data analysis. Ball roll distances obtained with the 38-cm Stimpmeter were converted to a standard USGA Stimpmeter (76-cm length) with methods described by Gaussoin et al. (1995).

Data Analysis
Data were subjected to analysis of variance. Clipping yield and seed-head cover were converted to percent of nontreated turf for results presentation with the equation

Formula
where responsex equaled response of treated turf and response0 equaled response of nontreated turf. Means were separated with Fisher's LSD test at a = 0.05. Orthogonal contrasts were performed on data so that inferences about TE regimens could be made for both species.


   RESULTS
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Turf Discoloration
Creeping bentgrass discoloration from TE was never observed (data not shown), but bermudagrass discoloration occurred in both years. A treatment-by-year interaction was detected for bermudagrass discoloration; results are presented separately by year. In 2003 all TE regimens caused unacceptable bermudagrass discoloration (>20%) 3 WAIT in May (Fig. 1 ). However, only bermudagrass treated with TE at 0.05 kg ha–1 3 wk–1 had unacceptable discoloration after sequential applications in June and July. Bermudagrass discoloration from the 0.017 kg ha–1 wk–1 regime was acceptable in 2004, while bermudagrass was discolored only once from the 0.033 kg ha–1 2 wk–1 regime. However, bermudagrass treated with TE at 0.05 kg ha–1 3 wk–1 in 2004 had unacceptable turf discoloration 1 wk after all sequential applications, but turf recovered by 2 wk after treatments.


Figure 1
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  		Figure 1. ‘TifEagle’ bermudagrass discoloration following trinexapac-ethyl applications beginning 1 May 2003 and 4 May 2004 in field experiments, Clemson, SC. Asterisks denote significant differences from nontreated turf at the 0.05 probability level.

 
Clipping Yield
Year-by-treatment interaction was not detected for creeping bentgrass clipping yield, but treatment-by-sampling date interaction was significant. Creeping bentgrass clipping yield reductions increased with TE rate 1 WAIT, but thereafter, results varied by TE regimen and sampling date (Fig. 2 ). Creeping bentgrass clipping yield was reduced from the nontreated on five, six, and six dates from weekly, biweekly, and triweekly TE application regimens, respectively. Postinhibition shoot growth enhancements were not detected from any TE regimen, but weekly TE applications at 0.017 kg ha–1 appeared to have less fluctuation in creeping bentgrass clipping yield compared with other application regimens over the 12 wk.


Figure 2
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  		Figure 2. Clipping yield reductions from nontreated for ‘L-93’ creeping bentgrass treated with trinexapac-ethyl from field experiments, 2003–2004, Clemson, SC. Asterisks denote significant differences from nontreated turf at the 0.05 probability level.

 
Treatment interactions with date and year were not detected for bermudagrass clipping yield; thus, results were pooled over all sampling dates. TifEagle bermudagrass treated with TE regimens had similar clipping yield reductions, averaging 55% of nontreated turf (Table 2 ).


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  		Table 2. Clipping yield reductions, seed-head suppression, and ball roll distances of ‘TifEagle’ bermudagrass treated with trinexapac-ethyl (TE) in field experiments, 2003–2004, Clemson, SC.

 
Seed-Head Suppression
Seed heads were never present on the creeping bentgrass green, but bermudagrass seed heads emerged in early summer of both years. Treatment-by-year interaction was not detected for bermudagrass seed-head suppression, so results were pooled over years. Seed-head coverage of nontreated plots averaged 58 and 10% in June 2003 and 2004, respectively. Bermudagrass seed-head suppression was similar for all TE regimens, averaging 80% in mid-June (Table 2).

Ball Roll
Treatment interactions with year and date were not detected for bermudagrass ball roll; thus, results were pooled over all sampling dates. For bermudagrass treated with TE, a.m. and p.m. ball roll distances increased 20 to 28 cm longer than a.m. distances of nontreated bermudagrass (Table 2). Ball roll was reduced by 10 cm from a.m. to p.m. for nontreated bermudagrass, but diurnal differences were masked by all TE regimens.

Root Mass
Treatment interactions with year and sampling date were not detected for root mass. Both creeping bentgrass and bermudagrass treated with TE had root mass similar to nontreated turf on all sampling dates (data not shown). Creeping bentgrass root mass declined by 48 and 67% from May to July of 2003 and 2004, respectively (data not shown). Bermudagrass root mass declined 52% from May to July in 2003 but was similar across dates in 2004 (data not shown).

Aerification Recovery
Year-by-treatment interaction was detected for bermudagrass aerification recovery; thus, years are presented separately. All TE treatments reduced bermudagrass recovery by 20 to 40% 1 wk after aerification (WAA) in May 2003; however, recovery was similar to nontreated turf by 2 WAA (Fig. 3 ). In 2004 the 0.05 kg ha–1 3 wk–1 TE regimen reduced aerfication recovery ?40% 1 and 2 WAA on 27 May. Bermudagrass receiving TE at 0.017 kg ha–1 wk–1 and 0.033 kg ha–1 2 wk–1 had similar aerification recovery to nontreated turf. Following the July 2003 aerification, turf recovery was reduced 20 to 30% by all TE regimens 1 WAA, but bermudagrass fully recovered by 2 WAA. Bermudagrass treated with TE had similar aerification recovery to nontreated turf in August 2004.


Figure 3
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  		Figure 3. Aerification recovery of ‘TifEagle’ bermudagrass treated with trinexapac-ethyl in field experiments, 2003–2004, Clemson, SC. Asterisks denote significant differences from nontreated turf at the 0.05 probability level.

 

   DISCUSSION
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Bermudagrass and creeping bentgrass putting greens require intensive management in the U.S. transition zone, but maintenance regimes must be modified for the species managed or player expectation. Although PGR use on hybrid bermudagrass has been investigated, practitioners require further information to develop PGR programs on dwarf bermudagrass golf greens because of genetic and morphological variations from cultivars used for fairways, tees, and roughs.

Creeping bentgrass discoloration from TE was never observed in this experiment, which is consistent with previous research (Fagerness et al., 2000; McCullough et al., 2006b). TifEagle bermudagrass was most sensitive to TE in May, but incremental weekly and biweekly applications helped mitigate turf discoloration from triweekly regimens without compromising total TE applied over 12 wk. Johnson (1994) noted similar leaf discoloration of Tifway bermudagrass following initial TE treatments of 0.2 kg ha–1 in late May, but turf generally recovered to acceptable levels within 1 to 2 wk. Fagerness and Yelverton (2000) also noted discoloration of Tifway bermudagrass from initial spring TE treatments at 0.11 kg ha–1, which was attributed to temperature in other experiments (Fagerness et al., 2002). Differences in tolerance to rates and interval of TE applications among species are likely due to growth and plant metabolism during late spring and early summer. Furthermore, triweekly applications of higher TE rates likely inhibited gibberellin synthesis to a greater extent following initial applications, which exacerbated dwarf bermudagrass discoloration from early summer applications (Pinthus et al., 1989). Results with TifEagle bermudagrass golf greens suggest applying triweekly TE regimens in weekly and biweekly increments at lower rates may effectively reduce these deleterious effects without reducing total TE rates applied.

While applying lower TE rates at more frequent application intervals effectively reduced bermudagrass discoloration, treatments resulted in similar clipping yield reduction, ball roll enhancement, and seed-head suppression compared with the triweekly regimen without restricting root growth. Clipping reductions from TE regimens resulted in ball roll distance enhancements in morning and evening that were greater than morning distances of nontreated turf over all dates. Results are consistent with other experiments on TifEagle bermudagrass with nitrogen and TE where evening distances of TE-treated turf were greater than morning distances of nontreated (McCullough et al., 2006a). In another study, creeping bentgrass ball roll distances were inconsistent over the 2 yr, but weekly, biweekly, and triweekly TE regimens enhanced ball roll on six, three, and four dates, respectively (McCullough et al., 2005).

Biweekly and triweekly TE applications on creeping bentgrass initially reduced clipping yield, but clippings were generally similar to nontreated turf on days of sequential applications. Weekly TE applications of 0.017 kg ha–1 did not initially or consistently reduce creeping bentgrass clipping yield, but fluctuation in clipping reductions appeared less substantial than other TE regimens. In other experiments, creeping bentgrass ball roll distances were infrequently enhanced, which was probably due to inconsistent clipping reductions (Fagerness et al., 2000; McCullough et al., 2006b). Results suggest that higher rates of TE could be applied more frequently on creeping bentgrass greens, such as 0.05 kg ha–1 biweekly, under moderate fertility regimes (6 kg N ha–1 wk–1) with spring and fall aerifications. However, the significance of TE effects could vary under different management regimes, such as routine topdressing, verticutting, or rolling, which warrants further investigation.

TifEagle bermudagrass produced greater seed heads in 2003 than 2004, which was likely the result of maturity and cooler spring temperatures in May 2003. Applications of TE reduced seed-head cover but did not completely suppress bermudagrass seed heads. Johnson (1994) noted that TE suppressed seed heads of higher-mowed bermudagrasses by >70%. In other experiments, TE provided partial seed-head suppression, but increased nitrogen fertility from 6 to 24 kg N ha–1 wk–1 reduced TifEagle bermudagrass seed-head coverage from 17 to 0% cover (McCullough et al., 2006c). Results suggest that TE and nitrogen fertility (>12 kg N ha–1 wk–1) during periods of seed-head formation would provide effective suppression on dwarf bermudagrass greens.

TifEagle bermudagrass recovery from aerifications was inhibited from TE applications. However, triweekly applications of TE at 0.05 kg ha–1 reduced aerfication recovery more frequently than weekly and biweekly regimens of lower rates. Inhibited aerification recovery from the triweekly TE regimen may have been exacerbated by bermudagrass foliar discoloration in both years. Conversely, incremental applications of weekly and biweekly TE treatments reduced discoloration and may have resulted in less-frequent recovery inhibition following aerifications. Previous studies noted that TifEagle bermudagrass lateral regrowth was inhibited by TE applications (Bunnell et al., 2005; McCullough et al., 2006c). These experiments also observed that increased nitrogen from 6 to 24 kg ha–1 wk–1 stimulated lateral growth, which improved recovery from aerifications. Results suggest that withholding TE before aerifications on bermudagrass golf greens while increased nitrogen fertility could enhance turf recovery. Since creeping bentgrass was aerified in spring and fall, effects of TE on aerification recovery were not measured during the test period, but further investigation is warranted.

Finally, conversion to improved species or cultivars may be desirable for putting greens in transition-zone golf courses. However, long-term TE use on bermudagrass greens will differ in rates and regimens from creeping bentgrass management. Managing TifEagle bermudagrass with TE in the transition zone may require lower rates than creeping bentgrass golf greens; creeping bentgrass managers could likely be more aggressive with TE use during spring and summer months. Further investigations are needed in the U.S. transition zone with other creeping bentgrass and dwarf bermudagrass cultivars. While these results have promising implications for TifEagle bermudagrass, further research should investigate effects of fertility, application timings, and mowing heights on responses of other dwarf bermudagrass cultivars, such as ‘Champion’ and ‘MiniVerde’, to these TE regimens.


   NOTES
TOP
 NOTES
ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Received for publication April 21, 2006.


   REFERENCES
TOP
 NOTES
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 




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C. M. Baldwin, H. Liu, L. B. McCarty, H. Luo, and J. E. Toler
Nitrogen and Plant Growth Regulator Influence on 'Champion' Bermudagrass Putting Green under Reduced Sunlight
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