St. Augustinegrass Response to Plant Growth Retardants

Abstract

St. Augustinegrass [(Stenotaphrum secundatum (Walt.) Kuntz.] is the preferred warm‐season turfgrass for Florida's commercial and residential landscapes with an estimated 0.7 million hectare under growth and management. Limited published information is available on St. Augustinegrass response to plant growth retardants (PGRs). A 2‐yr study was implemented to monitor St. Augustinegrass turf quality, lateral stolon growth, percent cover, mowing frequency, cumulative turfgrass clippings, and seedhead suppression following PGR application. Treatments were applied on 23 June 1995 and 22 June 1996 as a single application (SIA) at label use rate (LUR) or as twin split applications (TSA) at half LUR each: the sequential application was only used when mowing interval equaled the untreated. The PGRs and rates were flurprimidol [α‐(1‐methylethyl)‐α‐[4‐(trifluoro‐methoxy)phenyl]‐5‐pyrimidine‐methanol] and paclobutrazol [(+/−)‐(R*,R*)‐β‐[(4‐chloro‐phenyl)methyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol] at 1.12 kg ha−1 for SIA and 0.56 kg ha−1 for TSA, trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxocyclohexane carboxylic acid ethylester] and mefluidide [N‐[2,4‐dimethyl‐5‐[[trifluoromethyl)sulfonyl]amino]phenyl]acetamide] at 0.28 kg ha−1 for SIA and 0.14 kg ha−1 for TSA, and imazapic [(±)‐2‐[4,5‐dihydrol‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐methyl‐3‐pyridine‐carboxylic acid] at 0.028 kg ha−1 for SIA and 0.014 kg ha−1 for TSA. Responses were observed for a 12‐wk period following initial application, and turf quality was acceptable (>7) for all PGRs. Turf quality for imazapic was generally better than the untreated for Weeks 6 to 10. Greatest control of lateral stolon growth 10 wk after initial application was achieved with TSA of imazapic (68%) and mefluidide (61%). Percent cover 12 wk after initial application was lowest for SIA and TSA imazapic (66 and 53%, respectively). Greatest reduction in mowing frequency was provided by trinexapac‐ethyl (50%), while flurprimidol and mefluidide reduced mowing frequency by 26 and 20%, respectively. The only PGR that reduced cumulative turfgrass clippings (CTC) was trinexapac‐ethyl (63%). Greatest seedhead inhibition during peak production (about 35%) was provided by imazapic and mefluidide. The two most effective PGRs were trinexapac‐ethyl (reduced mowing frequency and CTC) and imazapic (controlled lateral stolon growth and seedhead production), while mefluidide demonstrated some potential. Combinations of these products could be examined in future studies.

Effect of plant regulators on growth and flowering of 'Meyer' zoysiagrass

“…Effect of plant regulators on growth and flowering of 'Meer' ... of 'Meyer' zoysiagrass immediately after the leaves were mowed for application of growth regulators (McCarty et al ., 2004;Waltz Jr. & Whitwell, 2005;Ervin & Zhang, 2007;McCullough et al, 2007). It should be noted that single doses of Type II growth regulators promote not only the obvious reduction in the concentration of gibberellins, but also an increase in the total chlorophyll b in the leaves up to two weeks after application.…”

“…In contrast, high doses provide better results for longer periods, but with higher levels of injury. This imbalance between efficiency and injury can be solved with sequential applications involving welladjusted doses (Fagerness & Yelverton, 2000;Lickfeldt, et al, 2001, McCarty et al, 2004Waltz Jr. & Whitwell, 2005;Ervin & Zhang, 2007;McCullough et al, 2007).…”

Produção de tapetes de grama Santo Agostinho submetida a doses de nitrogênio

“…Aos 296 DAC (setembro) houve aumento linear da ICV com as doses de N, sendo os valores, para as duas maiores doses de N (450 e 600 kg ha -1 ), 49,7 a 50,7 unidades SPAD, superiores aos citados como adequados, para a grama Esmeralda, por Godoy et al (2007a). A grama Santo Agostinho possui folhas com coloração verde mais intensa que a Esmeralda, o que lhe confere maior tolerância ao sombreamento (MCCARTY et al, 2004) e por isso, os valores foram maiores. Rodriguez e Miller (2000) encontraram fortes correlações entre os valores de ICV e a concentração de clorofila (r 2 = 0,79), índice de qualidade visual do gramado (r 2 = 0,74) e a concentração de N na folha (r 2 = 0,71) da grama Santo Agostinho.…”

Growth inhibitors in turfgrass

“…High doses have the opposite effects, e.g., they reduce plant height for longer periods of time but with high levels of injury. This unbalance between efficiency and injury may be resolved by the sequential application of betteradjusted doses (Fagerness & Yelverton, 2000;Lickfeldt et al, 2001;McCarty et al, 2004;Waltz Jr & Whitwell, 2005;Ervin & Zhang, 2007;McCullough et al, 2007).…”

“…The rapid recovery in height after plant cutting and single application of growth inhibitors is due, at first, to the non-structural carbohydrates redistribution which were stored in grass stolons and rhizomes soon after leaves had been cut for the application of growth regulators (McCarty et al, 2004;Waltz Jr. & Whitwell, 2005;Ervin & Zhang, 2007;McCullough et al, 2007). It is noteworthy that single doses of growth inhibitors of classes A and B promote not only the reduction in gibberellins concentration, but also the increment of the total concentration of chlorophyll b in plant leaves up to two weeks after product application.…”