Plant Growth Regulators and Mowing Height Affect Ball Roll and Quality of Creeping Bentgrass Putting Greens

Abstract

<jats:p>Questions exist as to whether growth-inhibiting chemicals mimic the effects of reduced mowing heights on putting green ball roll. An experiment was initiated during Spring 1997 to investigate ball roll and visual quality parameters of putting greens maintained at 3.2, 4.0, or 4.8 mm with plant growth regulator (PGR) treatments applied monthly over the course of 1 year. Additional experiments were conducted during Fall 1995 and 1996 and Spring 1996 to investigate diurnal PGR effects on ball roll. All experiments were conducted on pure stands of `Penncross' creeping bentgrass (<jats:italic>Agrostis palustris</jats:italic> Huds). Treatments included trinexapac-ethyl and paclobutrazol, both inhibitors of gibberellin biosynthesis. In the one-year experiment, mowing height was inversely related to ball roll. However, compromises in turfgrass visual quality and shoot density in `Penncross' turf mowed at 3.2 mm make this a questionable mowing height in areas with severe summer conditions. Ball roll during summer months was reduced by PGRs, suggesting that PGRs have little potential as alternatives to decreasing mowing height for increased ball roll. Paclobutrazol reduced turfgrass quality and shoot density during summer months, suggesting that it be used with caution. Other PGRs, particularly trinexapac-ethyl at 0.05 kg·ha<jats:sup>–1</jats:sup> a.i., increased afternoon ball roll by as much as 5% to 10% in diurnal experiments. Use of PGRs on creeping bentgrass putting greens may therefore produce short-lived increases in ball roll with subtle to negative effects on bentgrass growth over more extended periods of time. Chemical names used: 4-(cyclopropyl-α-hydroxymethylene)-3,5-dioxocyclohexane carboxylic acid ethylester (trinexapac-ethyl); (+/–)-(<jats:italic>R</jats:italic><jats:sup>*</jats:sup>,<jats:italic>R</jats:italic><jats:sup>*</jats:sup>)-β-[(4-chloro-phenyl)methyl]-α-(1,1dimethylethyl)-1<jats:italic>H</jats:italic>-1,2,4-triazole-1-ethanol (paclobutrazol).</jats:p>

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

“…Also, RB recovery in turf mowed to a height of 3.2 mm may be both initially less in magnitude and ultimately shorter in duration than at higher mowing heights. Such a response following periods of summer stress may be related to reduced quality and shoot density in creeping bentgrass mowed to a height of 3.2 mm during summer months (Fagerness et al, 2000).…”

“…Penncross creeping bentgrass had lower RB when mowed to a height of 3.2 mm than when mowed at either 4.0 or 4.8 mm heights, suggesting that Penncross should not be maintained below 4.0 mm, particularly during the summer (Table 2). Observed summer decline in shoot density of Penncross mowed to a height of 3.2 mm (Fagerness et al, 2000) may explain why autumn RB recovery started slower and ended sooner at the low mowing height (Table 2). Since RB was equal between bentgrass mowed to a height of 4.0 and 4.8 mm (Table 2), and because measured putting green speed is increased when lowering mowing height from 4.8 to 4.0 mm (Fagerness et al, 2000), there was no apparent benefit of mowing bentgrass to a 4.8 mm height.…”

“…Observed summer decline in shoot density of Penncross mowed to a height of 3.2 mm (Fagerness et al, 2000) may explain why autumn RB recovery started slower and ended sooner at the low mowing height (Table 2). Since RB was equal between bentgrass mowed to a height of 4.0 and 4.8 mm (Table 2), and because measured putting green speed is increased when lowering mowing height from 4.8 to 4.0 mm (Fagerness et al, 2000), there was no apparent benefit of mowing bentgrass to a 4.8 mm height. Considering Penncross quality when mowed to a 4.0 mm height is greater than at a 3.2 mm mowing height, the 4.0 mm mowing height may be ideal for this cultivar in areas with severe summer stress (Fagerness et al, 2000; Huang et al, 2000).…”

Ethephon and Trinexapac-ethyl Influence Creeping Bentgrass Growth, Quality, and Putting Green Performance

“…Responses, such as these, would likely negatively influence creeping bentgrass surface uniformity and may explain a lack of ball‐roll distance enhancements despite clipping yield reductions. In experiments on ‘Penncross’ creeping bentgrass greens, Fagerness et al (5) noted TE enhanced ball‐roll distances while applications of paclobutrazol, an early gibberellin synthesis inhibitor, did not. These experiments suggest shoot growth inhibition following applications of various PGRs may not necessarily enhance ball‐roll distances since other physiological responses to growth regulation may influence putting green surface uniformity.…”

“…Maintaining turfgrasses under conditions that challenge their physiological capacities, such as from these mechanical methods, may have deleterious effects on root growth, turf vigor, and recuperative capabilities from disease, traffic, heat, and other environmental stresses (12). Applying a plant growth regulator (PGR), trinexapac‐ethyl (TE), reduces uneven shoot growth to improve ball‐roll distances without negatively affecting turfgrass health (5). Applications of TE also enhance creeping bentgrass stress tolerances, increase tillering, and increase chlorophyll concentrations (8,9).…”